UNIVERSITY   OF    CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT   STATION 

BERKELEY,    CALIFORNIA 


POULTRY  FEEDING:  PRINCIPLES 
AND  PRACTICE 

WALTHER  F.  HOLST  and  WILSON  E.  NEWLON 


BULLETIN  417 

February,  1927 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1927 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/poultryfeedin4171927hols 


POULTRY  FEEDING:   PRINCIPLES  AND   PRACTICE 

WALTHEE  F.  HOLSTi  and  WILSON  E.  NEWLON2 


PRINCIPLES  OF  POULTRY  FEEDING 

The  production  of  eggs  and  market  poultry  is  a  process  of  trans- 
forming comparatively  cheap  feeds  into  high-priced  products  for 
human  consumption.  The  fowl's  body  is  the  agent  which  effects  this 
transformation.  Under  the  highly  specialized  conditions  of  com- 
mercial egg  production  in  California,  the  poultryman  cannot  expect 
the  greatest  efficiency  from  his  birds  without  a  working  knowledge  of 
the  principles  of  animal  nutrition.  Poultry  feeding  should  be  based 
on  the  food  requirements  of  the  birds,  the  nutritive  value  of  the 
different  feeds  and  a  knowledge  of  how  to  use  these  with  particular 
objects  in  view. 

NECESSITY    FOR    FOOD 

Although  plants  can  nourish  themselves  from  such  simple  sources 
as  soil  and  air,  domestic  birds,  like  all  other  animals,  require  ready- 
made  nutrients.     They  utilize  these  for  two  main  purposes : 

1.  As  building  material  for  the  construction  of  new  tissues  and 

their  products. 

2.  As  a  source  of  heat  and  energy. 

At  all  times  newly  formed  tissue  is  needed  for  replacement  of  the 
tissue  destroyed  by  the  general  wear  and  tear  of  the  body.  Cells  (i.e., 
the  small  units  of  which  the  tissues  of  the  body  are  composed),  are 
constantly  being  worn  out,  broken  down  and  sloughed  off.  These 
cells  have  to  be  replaced  by  material  from  the  outside.  During  cer- 
tain periods  new  tissue  is  needed  also  for  growth  and  reproduction; 
that  is,  for  the  formation  of  new  body  material  and  reproductive  cells. 
The  body  also  needs  energy  for  the  production  of  heat,  which  is 
necessary  to  maintain  the  body  temperature  and  for  all  the  body 
activities,  including  locomotion,  blood  circulation,  respiration,  diges- 
tion, absorption  and  excretion.  These  activities  are  the  distinguishing 
characteristics  of  what  is  called  animal  life,  and  all  consume  energy. 


1  Assistant  Poultry  Husbandman,  Agricultural  Experiment  Station. 

2  Poultry  Specialist,  Agricultural  Extension  Service. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

For  these  purposes  birds  need  a  constant  supply  of  food.  If  this 
supply  should  fail  for  any  length  of  time  the  birds  would  begin  to 
lose  weight,  living  on  and  consuming  their  own  body  material  until 
death  occured.  This  usually  happens  within  about  34  days,  during 
which  time  there  is  a  loss  of  body  weight  of  from  20  to  50  per  cent.  If, 
on  the  other  hand,  the  supply  exceeds  the  demand ;  that  is,  more  food 
is  provided  than  is  required  for  these  activities,  the  body  has  the  power 
to  store  the  excess  digested  food  as  body  fat.  Body  fat  is  nature's 
provision  of  a  reserve,  in  case  the  food  supply  should  fail  partly  or 
completely  for  a  short  period. 

Food  is  composed  of  several  distinctly  different  groups  of  sub- 
stances, which  are  called  nutrients.  Of  these  the  following  six  groups 
are  recognized :  proteins,  carbohydrates,  fats,  vitamins,  minerals,  and 
water. 

DIGESTION    OF    FOOD 

Most  of  the  nutrients  cannot  be  used  by  the  birds  in  the  form  in 
which  they  are  supplied  in  the  food.  They  must  undergo  digestion, 
which  means  breaking  them  down  into  their  very  simplest  and  most 
soluble  forms,  so  that  they  can  pass  through  the  intestinal  wall,  be 
absorbed  by  the  blood,  and  distributed  through  the  body.  Digestion 
is  made  possible  by  the  agency  of  various  chemical  substances,  called 
enzymes  or  ferments.  These  are  supplied  in  the  digestive  juices,  and 
partly,  also,  in  ordinary  feeds.  Digestion  in  birds  is  very  rapid. 
Complete  digestion  of  grains  requires  from  ten  to  fifteen  hours  while 
digestion  of  mash  requires  from  two  and  a  half  to  four  hours  only. 

NUTRIENTS 

Proteins. — Protein  is  the  name  of  a  group  of  very  complex  organic 
substances,  which  always  contain  carbon,  hydrogen,  oxygen,  and 
nitrogen.  Proteins  usually  also  contain  sulphur  and  frequently  phos- 
phorous. These  substances  are  widely  distributed,  both  in  plants, 
which,  as  indicated,  build  them  up  from  simple  sources  in  the  soil 
and  air,  and  in  animal  tissues,  which  must  derive  them  directly  or 
indirectly  from  plant  tissues.  The  thousands  of  different  known 
forms  of  protein  vary  widely  in  character  but  have  two  characteristics 
in  common;  they  all  contain  nitrogen  in  a  definite  proportion  (16 
per  cent)  and  all  are  composed  of  certain  simpler  building-stones,  the 
amino  acids. 

A  bird's  body  contains  as  much  protein  as  all  other  groups  of 
nutrients  together,  if  water  is  excepted.    Twenty  per  cent  of  the  live 


BUL.  417]  POULTRY    FEEDING:    PRINCIPLES    AND    PRACTICE  5 

weight  and  practically  50  per  cent  of  the  dry  weight  is  protein.  It  is 
therefore  easy  to  understand  the  importance  of  this  group  of  nutrients 
in  feeding. 

Of  the  amino  acids  which  form  the  proteins,  about  twenty  are 
known.  Certain  of  the  amino  acids  are  more  important  from  the 
standpoint  of  feeding  practice  than  others.  This  is  because  some  of 
them,  such  as  tryptophane,  lysine,  and  cystine  cannot  be  built  up  by 
fowls  from  other  amino  acids,  while  certain  others,  such  as  glycocol, 
can  be  formed  in  the  bird 's  body  from  the  excess  of  other  amino  acids 
present. 


y 

/ 

f 

s 

/' 

.~y 

<f 

■/ 

s 

i 
1 

f 

** 

s 

^ 

1 
1 

Zei 

■»   *■    T 

"ypi-op 

hone 

X 

^ 

+ZOdoys-* 

Fig.  1. — Comparison  of  growth  on  complete  and  incomplete  proteins 
(after  Mendel). 


Figure  1  illustrates  the  changes  in  body  weight  of  rats  fed  on  poor 
proteins ;  that  is,  proteins  lacking  in  one  or  more  of  the  essential 
amino  acids.  In  the  case  which  supplied  the  data  Indian  corn  was 
the  only  source  of  protein.  The  protein  part  of  corn,  which  is  called 
zein,  is  known  to  be  lacking  in  the  two  amino  acids,  tryptophane  and 
lysine.  Not  until  those  two  were  added  did  growth  take  place.  The 
addition  of  tryptophane  only  was  sufficient  to  maintain  body  weight, 
but  growth  did  not  begin  until  lysine  was  added  also.  Exactly  similar 
results  would  be  expected  if  chicks  were  used.  Other  grain  proteins 
have  similar  deficiencies. 

To  be  complete  and  give  the  best  results  as  a  food,  a  protein  must 
contain  all  of  these  essential  amino  acids.  Naturally  the  necessary 
amino  acids  may  be  provided  by  a  combination  of  properly  chosen 
incomplete  proteins.     Proteins  in  the  form  in  which  they  are  present 


b  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

in  the  feed  are  of  no  value  to  the  birds ;  as  indicated  in  figure  2,  they 
have  to  be  broken  down  by  digestion  into  the  amino  acids,  which  are 
soluble  and  therefore  can  be  absorbed  by  the  blood.  The  blood  carries 
the  amino  acids  to  different  parts  of  the  body,  where,  according  to  the 
bird's  needs,  they  are  put  together  again  into  new  proteins,  the  body 
proteins. 


CRUPE  FOOD  PROTEINS 


Undigested 
Food 


Digestive  Tract 


Amino  Acids 


Body 


i 


Body  Protein 


Excess  Amino  Acids 


Uric  Acid,  Urea 
Ammonia,  etc. 


Nitrogen  Part   Carbohyt rate  Part  Fat  Par + 


Liver  6iycogen         Body  Fat 


I 


1 


Muscle  6 iy coy  en 


k-. 


1 


Fgg  Protein  +  Fot 


Burned  (Oxidized)  ] 
I  for  tfeat  r  Energy  \ 
~lr 


«j 


*■  no 


Fig.  2. — Scheme  illustrating  the  use  of  proteins  in  the  body. 

If  protein  is  provided  in  excess  of  requirements,  the  amino  acids 
are  formed  and  absorbed  by  the  blood  as  usual.  In  the  liver,  however, 
they  are  deprived  of  their  nitrogen,  thus  being  transformed  into  one 
or  both  of  two  other  classes  of  nutrients,  carbohydrates  and  fats.  The 
fate  of  the  tissue  protein  after  it  is  worn  out  is  similar.  It  is  broken 
down  into  amino  acids,  which  are  then  deprived  of  their  nitrogen,  the 
remaining  part  being  used  in  the  animal  organism.  The  nitrogen  thus 
separated  from  the  amino  acids  does  not  appear  in  the  free  form,  but 
is  normally  split  off  as  ammonia,  which  is  transformed  inside  the 
bird 's  liver  into  uric  acid  and  urea,  substances  which  are  then  expelled 
as  parts  of  the  urine  through  the  kidneys.  A  diet  too  high  in  protein, 
therefore,  puts  an  unnecessary  and  dangerous  burden  on  these  organs. 


BUL.  417]  POULTRY    FEEDING  :    PRINCIPLES    AND    PRACTICE  7 

As  indicated  above,  excess  of  protein  in  a  feed  is  not  wholly  wasted. 
The  nitrogenous  part  is  wasted,  but  the  rest  becomes  carbohydrates 
and  fats.  While  protein  can  thus  replace  carbohydrates  or  fats  to  a 
certain  degree,  the  reverse  is  not  possible,  because  these  latter  nutrients 
do  not  contain  nitrogen  and  are  not  capable  of  taking  it  up.  A  lack 
of  protein  in  a  ration  may  lead  to  cannibalism,  which  in  that  case  is 
merely  an  expression  of  the  craving  for  protein. 

Carbohydrates. — These  organic  compounds  contain  only  three 
chemical  elements :  carbon,  hydrogen,  and  oxygen.  The  last  two  ele- 
ments nearly  always  appear  in  the  same  proportions  as  they  exist 


Food  Carbohydrates 


Digest i\ 


e  Tract 


Simple  5ugars 


Body 


L 


1 


Undigested 
Food 


Liver  Glycogen 


I 


1 


Body  Fat 


Muscle  6lc/cogen 


x 1 , 

I  Burned  (Oxidized)  j 
\ibr  Heat  t  Energy 


Egg  Fat 


CQsHJ) 


Fig.  3. — Scheme  illustrating  the  use  of  carbohydrates  in  the  body. 


in  water,  in  fact,  the  name  carbohydrate  means  carbon-water.  The 
carbohydrate  group  includes  the  starches,  sugars,  and  celluloses.  The 
celluloses,  however,  are  generally  classed  separately  under  various 
headings  as  "fiber,"  "crude  fiber,"  etc.,  in  tables  giving  the  composi- 
tion of  feeds.    The  crude  fiber  is  wholly  indigestible  for  poultry. 

In  the  course  of  digestion  the  carbohydrates  as  shown  in  figure  3, 
are  broken  down  into  the  simplest  kind  of  sugars,  the  so-called  mono- 
saccharids,  in  which  form  they  are  absorbed.  The  monosaccharids 
readily  combine  with  oxygen  (which  is  absorbed  from  the  lungs  by  the 
haemoglobin  of  the  blood)  ;  they  are  thus  oxidized  (or  burned)  to 
carbon  dioxide  and  water  with  the  production  of  heat.  Upon  this 
heat  liberation,  as  already  mentioned,  the  different  life  processes  of 
birds,  as  of  other  animals,  are  absolutely  dependent. 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  scarcity  of  carbohydrates  in  the  animal  body  and  their  pre- 
ponderance in  the  feeds  indicate  that  they  are  stored  only  temporarily 
as  carbohydrates  and  are  either  nsed  comparatively  soon,  serving  as 
fuel  for  the  animal  organism,  or  for  the  most  part  stored  in  some 
other  form  (fat,  see  below).  They  are  found  stored  in  certain  tissues, 
however.  This  is  because  the  body  requirements  for  fuel  vary  widely, 
being  high  during  vigorous  exercise  and  low  during  rest  and  sleep. 
The  liver  acts  as  a  regulator  of  this  fuel  supply.  As  the  blood,  with 
the  dissolved  sugars,  passes  from  the  intestines  on  its  way  to  the  heart, 
it  circulates  through  the  liver,  where  excess  sugars  are  deposited,  to 
be  stored  in  the  form  of  animal  starch  or  glycogen.  This  carbohydrate 
is  also  stored  in  the  muscles. 

After  feeding  and  during  rest  this  starch  may  compose  as  much 
as  15  per  cent  of  the  weight  of  the  liver.  At  other  times,  as  during 
starvation  or  after  vigorous  exercise,  it  may  be  found  to  compose  as 
little  as  2  per  cent  of  this  organ.  The  muscles  normally  contain  about 
0.6  per  cent  of  glycogen,  the  total  amount  in  all  the  muscles  of  the 
body  being  approximately  equal  to  that  in  the  liver.  When  any  muscle 
or  organ  of  the  body  is  used,  a  supply  of  energy  in  the  form  of 
glycogen  is  present  within  the  particular  muscle  or  organ  of  which 
work  is  required.  The  glycogen  is  broken  down  and  oxidized,  setting 
free  the  necessary  energy.  The  muscles  then  immediately  begin  to 
draw  on  the  main  reserve  of  glycogen  in  the  liver  for  the  replenishing 
of  their  supply.  The  liver  in  turn  receives  its  replacements  from 
the  food. 

Consequently  the  liver  is  not  only  a  storage  place  for  but  also  the 
regulator  of  the  carbohydrate  supply.  It  stores  the  excess  sugar  after 
meals  and  later  gives  it  up  to  the  blood  which  distributes  it  to  the 
different  body  parts  according  to  demand. 

pats. — These  are  compounds  of  an  alcohol  (usually  glycerin)  and 
the  fatty  acids  (commonly,  stearic,  palmitic  and  oleic  acid).  Like 
carbohydrates  they  contain  only  the  three  elements,  carbon,  hydrogen, 
and  oxygen.  They  differ  from  carbohydrates  in  that  oxygen  is  con- 
tained in  much  smaller  proportions.  (Starch  and  sugars  contain 
between  49.4  and  53.3  per  cent;  fats  on  the  other  hand  contain  about 
11.0  per  cent  oxygen.) 

In  the  body,  fats  from  the  food  are  broken  down  (digested)  to 
free  fatty  acids  and  glycerin,  as  illustrated  by  figure  4,  which  pass 
through  the  intestinal  wall,  immediately  to  be  recombined  into  fats. 
These  are  taken  up  by  and  pass  along  with  the  blood  in  a  suspended 
form.     The  fats  are  used  for  energy  purposes,  probably  being  first 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE  9 

transformed  into  sugars,  which  then  combine  with  more  oxygen,  pro- 
ducing heat,  carbon  dioxide,  and  water.  If  not  needed  immediately  as 
a  source  of  energy  they  are  deposited  within  the  cells  and  in  the 
so-called  adipose  or  fatty  tissue.  This  is  found  below  the  skin,  in  the 
folds  of  the  abdominal  cavity,  and  as  protective  layers  around  certain 
vital  organs  like  the  kidneys. 

Body  fats  are  also  derived  from  another  source.  Since  the  storage 
places  for  carbohydrates,  the  liver  and  muscles,  soon  become  loaded  to 
their  limit,  a  transformation  process  sets  in,  changing  carbohydrates 
into  fats.     Carbohydrates  in  excess,  therefore,  produce  body  fats,  and 


Food  Fat 


Digestive  Tract 
\6lycerin  + Fatty  Acids 


Body 


I 


Undigested 
Food 


Fat  in  Bfood 


I 


Body  Fat 


JL 


I 


J  Burned  (Oxidized)  \      \Fgg  Fat 
i  For  Heat  •+  Fnergy^ 


Fig.  4. — Scheme  illustrating  the  use  of  fats  in  the  body. 

fats  under  certain  conditions  are  transformed  back  to  carbohydrates. 
Approximately  two  and  one-fourth  parts  of  carbol^drates  yield  one 
part  of  fat,  or  one  part  of  fat  corresponds  to  two  and  one-fourth  parts 
of  carbohydrates. 

This  difference  is  due  to  the  fact  mentioned  above,  namely,  that 
fats  contain  less  oxygen  than  do  carbohydrates.  The  presence  of 
oxygen  in  a  compound  always  indicates  that  some  oxidation  (burning) 
has  already  taken  place.  The  more  oxygen  present  in  a  compound, 
therefore,  the  less  energy  will  be  liberated  on  complete  oxidation 
(burning  to  carbon  dioxide  and  water).  Or  stating  the  reverse,  the 
less  oxygen  there  is  present,  the  more  energy  will  be  liberated. 

Animals  do  not  create  any  energy.  Therefore  they  use  two  and 
one-fourth  parts  of  carbohydrates  to  produce  one  part  of  fat,  losing 


10  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

oxygen  in  the  process.  Fats  on  the  other  hand  form  carbohydrates, 
taking  np  oxygen  and  thereby  increasing  their  weight  and  giving  off 
heat. 

It  is  a  matter  of  common  knowledge  that  in  the  fattening  of  poultry 
and  other  domestic  animals,  not  fats  but  carbohydrates,  are  fed  in 
excess.  This  is  because  carbohydrates  even  in  large  quantities  are  very 
easily  digested,  absorbed,  and  transformed  into  fat  with  practically  no 
loss  of  energy.  Fats,  on  the  other  hand,  are  digested  only  with  diffi- 
culty, and  are  absorbed  slowly.  Such  are  the  difficulties  that  large 
proportions  of  fat  in  the  food  may  retard  and  upset  the  normal  meta- 
bolism of  the  other  nutrients.  Consequently  large  amounts  of  fat  are 
always  avoided  in  animal  feeding.  The  amount  that  birds  can  handle 
and  make  proper  use  of  increases  with  the  exercise  they  have  and  the 
coldness  of  the  weather  to  which  they  are  exposed. 

Vitamins. — There  are  five  known  members  of  this  group  of 
nutrients,  called  by  the  first  letters  of  the  alphabet,  A,  B,  C,  D,  and  E. 
Recent  investigations  indicate  that  doubtless  there  are  still  others, 
but  not  enough  is  known  of  them  to  warrant  discussion.  The  physio- 
logical importance  of  the  vitamins  in  life  and  their  main  sources  are 
well  known,  but  their  chemical  composition  is  still  a  mystery. 
Vitamins  are  characterized  by  the  lack  of  proportion  between  their 
great  importance  in  nutrition  and  the  extremely  small  quantities  in 
which  they  are  normally  required.  The  quantities  in  which  they  are 
present  in  food  are  far  too  small  to  contribute  to  the  body  any  energy 
worth  mentioning.  It  is  so  far  unknown  whether  the  vitamins  are 
actual  building  stones  (structural  components)  of  the  body,  or  whether 
they  are  simple  catalysts  (accelerators)  which  speed  up  certain  essen- 
tial body  processes.  It  has  been  found,  however,  that  if  certain  very 
small,  indeed  minute,  parts  are  removed  from  an  adequate  ration,  this 
ration  fails  to  support  life.  If  they  are  removed  for  any  length  of 
time,  the  result  is  inevitably  disease  (so-called  deficiency  disease)  and 
eventually  death.  On  the  other  hand  this  failure  may  be  prevented  or 
health  may  be  restored  if  these  small  parts,  which  were  withdrawn 
from  the  adequate  ration,  are  again  added  to  it.  Unlike  the  other 
classes  of  nutrients  which  are  very  stable  chemical  compounds,  the 
vitamins  are  all  more  or  less  unstable,  which  makes  their  study  much 
more  difficult.  Because  of  this  instability,  care  must  always  be  taken 
to  ensure  an  adequate  supply  of  vitamins  in  poultry  rations.  When 
the  individual  needs  have  been  covered,  an  excess  can  in  certain  cases 
be  stored  (see  p.  11)  in  the  animal  tissues.  A  supply  of  any  of  the 
vitamins  discussed  beyond  that  which  is  needed  and  that  which  can 


BUL.  417]  POULTRY   FEEDING:    PRINCIPLES   AND    PRACTICE 


11 


be  stored  by  the  body,  is  either  destroyed  or  excreted.    In  no  case  has 
any  benefit  to  the  bird  from  such  an  excess  been  demonstrated. 

Vitamin  A  (or  fat-soluble  A)  is  also  called  the  growth  vitamin, 
because  one  of  its  main  effects  seems  to  be  that  of  promoting  growth  in 
young  stock.  Animals  fed  on  an  otherwise  perfect  ration,  but  lacking 
this  vitamin  stop  growing.  Examples  of  this  effect  are  shown  in  the 
growth  records  in  figure  5.  Another  condition  also  results,  namely  an 
eye  disease  called  zerophthalmia,  meaning  dryness  of  the  eye.  Not 
only  the  secretory  glands  of  the  eye,  but  also  those  of  the  mouth,  nose, 
and  throat  dry  up.  As  the  secretions  of  these  glands  are  germicides 
to  some  extent,  infections  in  these  locations  are  frequent  when  the 


Fig.  5. — Growth  with  and  without  Vitamin  A  (after  Hopkins). 


ration  is  deficient  in  vitamin  A.  This  condition,  sometimes  called 
nutritional  roup,  always  is  caused  by  a  vitamin  A  deficiency  and  can 
always  be  prevented  or  cured  by  the  feeding  of  substances  known  to. 
be  good  sources  of  this  vitamin,  as  shown  by  Beach3  (1924)  and  Davis 
and  Beach  (1925). 

Vitamin  A  is  synthesized  (built  up)  by  plants  and  is  found  in 
green  food  and  also  to  a  less  extent  in  the  embryos  of  many  seeds,  as 
millet,  linseed,  and  yellow  corn.  It  is  also  found  in  tomatoes  and 
yellow  carrots.  The  vitamin  is  not  present  in  white  corn,  white  leaves 
of  plants,  or  in  most  root  crops.  Other  good  sources  are  certain 
animal  fats,  such  as  butterfat,  egg-yolk  fat,  and,  best  of  all,  a  good 
grade  of  cod-liver  oil. 

Although  vitamin  A  is  synthesized  in  plants  it  cannot  be  syn- 
thesized by  animals,  but  appears  in  animal  fats  because  of  the  ability 
of  the  animals  to  store  it.     The  significance  of  this  storing  ability  is 


3  Full  citations  of  these  and  similar  references  given  in  this  publication  will  be 
found  in  the  bibliography,  page  47. 


12  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

great ;  it  enables  the  hen  to  provide  her  chicks  with  a  high  concentra- 
tion of  this  vitamin  in  the  egg  yolk.  Young  mammals  get  their  supply 
in  a  similar  way  through  the  milk.  But  because  the  vitamin  cannot 
be  synthesized,  in  animal  tissues,  the  amount  present  will  always 
depend  upon  the  amount  provided  in  the  food. 

When  vitamin  A  is  exposed  to  the  air,  particularly  at  temperatures 
above  room  temperature,  it  is  very  unstable,  being  rapidly  oxidized. 
If  cod-liver  oil  is  not  kept  in  closed  containers,  the  vitamin  A  in  it 
is  soon  destroyed.  On  the  other  hand,  this  vitamin  is  well  preserved 
in  plants,  like  alfalfa,  when  the  curing  conditions  are  favorable ;  that 
is,  when  the  drying  is  accomplished  rapidly,  but  without  exposure  to 
excessively  high  temperatures. 

Vitamin  B  (also  called  water-soluble  B  or  the  anti-neuritic  factor) 
is  without  question  the  most  widely  distributed  of  all  vitamins.  It 
appears  in  the  germ  and  bran  of  all  grains,  and  also  in  fresh  vegetables 
and  green  feed,  milk,  and  egg  yolk.  Yeast  is  a  particularly  good 
source. 

A  dietary  deficiency  with  regard  to  this  vitamin  causes  a  nervous 
disorder  in  poultry,  called  avian  polyneuritis,  which  is  physiologically 
equivalent  to  human  beri-beri.  Both  diseases,  the  avian  as  well  as  the 
human,  develop  paralysis  of  the  limbs,  at  times  edema,  and  finally  heart 
failure.  The  earliest  result  of  a  deficiency,  however,  is  an  immediate 
and  marked  decrease  in  the  food  consumption  of  the  animal,  so  that 
any  disturbance  with  regard  to  the  vitamin  B  supply  may  be  sufficient 
to  throw  an  animal  out  of  condition.  The  fact  that  vitamin  B  is 
present  in  practically  all  common  poultry  feeds  is  probably  due  to  the 
greater  stability  of  this  substance.  Exposure  to  air  and  even  quite 
long  heating  do  not  destroy  it. 

Vitamin  C  (also  called  water-soluble  C  or  the  antiscorbutic 
vitamin)  is  of  little  importance  in  poultry  feeding,  as  fowls  seem  to  be 
able  to  build  up  sufficient  amounts  of  this  substance  in  the  liver, 
kidneys,  and  other  organs.  It  prevents  a  disease  known  as  scurvy,  to 
which  domestic  birds  do  not  seem  to  be  susceptible. 

Vitamin  D  is  known  as  the  antirachitic  factor.  It  is  perhaps  the 
most  peculiar  of  these  newly  discovered  substances,  since  its  place 
may  be  taken  by  a  purely  physical  agent — certain  light  rays.  It  is  con- 
tained in  a  few  animal  fats  where  it  often,  though  not  always,  occurs 
associated  with  vitamin  A.  The  outstanding  source  of  both  of  these  is 
cod-liver  oil.  Vitamin  D  may  also  under  certain  conditions  be  con- 
tained in  cured  hay.  It  is  not  found  in  the  fresh  green  plant,  but 
seems  to  be  formed  during  the  curing  process  if  there  is  long  exposure 
to  the  sunlight,  a  condition  under  which  vitamin  A  is  destroyed. 


BUL.  417]  POULTRY   FEEDING :    PRINCIPLES   AND   PRACTICE  13 

The  best  known  abnormality  caused  by  a  lack  of  this  vitamin  is  a 
bone  disease  called  rickets.  The  most  prominent  characteristic  of  this 
disease  is  a  disturbance  of  the  utilization  and  retention  of  lime  salts 
in  the  body.  Lime  salts,  of  which  calcium  phosphate  is  one  of  the 
most  important,  are  either  not  deposited,  or  are  deposited  to  an  insuffi- 
cient degree  in  the  growing  bone,  the  result  being  many  forms  and 
degrees  of  deformities.  Provided  with  an  abundance  of  calcium  in  the 
diet,  the  bird  cannot  make  use  of  it  unless  the  antirachitic  factor 
(vitamin  D  or  certain  light  rays)  is  also  provided.  Lack  of  this  factor 
inevitably  results  in  poor  bone  formation.  A  mineral  deficiency 
obviously  will  have  the  very  same  result.  Unless  minerals  are  present, 
no  minerals  can  be  deposited,  but  even  a  large  excess  of  lime  salts  is 
of  no  use  to  the  bird  without  the  cooperation  of  the  vitamin  D  or  the 
light  rays  mentioned  above. 

These  rays  are  usually  referred  to  as  the  ultra-violet  rays  or  ultra- 
violet light.  They  are  rays  of  comparatively  short  wave  length  found 
in  sunlight  and  may  be  produced  artificially  by  means  of  the  so-called 
ultra-violet  lamp.  These  rays  prevent  or  cure  rickets  just  as  effectively 
as  does  vitamin  D. 

The  disease  generally  affects  the  growing  stock,  in  which  it  is  called 
leg  weakness.  Adult  birds  may  also  suffer  from  the  same  disease. 
The  effort  of  laying  birds  to  produce  normal  eggs  is  so  intense  that 
they  actually  deprive  their  own  bones  of  calcium,  and  may  develop 
severe  cases  of  rickets  unless  the  factor  which  controls  the  utilization 
of  lime,  is  also  provided  in  sufficient  amount.  The  crooked  breast 
bones  observed  in  good  layers  are  often  a  result  of  this  condition. 

The  antirachitic  vitamin,  although  not  as  unstable  as  vitamin  A, 
is  also  affected  by  prolonged  oxidation  and  high  temperature. 

Vitamin  E  is  closely  connected  with  the  functions  of  the  reproduc- 
tive organs  of  animals.  The  only  experimental  work  done  so  far  with 
this  vitamin  has  been  with  rats,  but  presumably  similar  results  would 
be  obtained  with  birds.  This  vitamin  seems  more  essential  to  the 
males,  where  a  continued  deficiency  may  produce  permanent  sterility. 

Vitamin  E  is  contained  in  many  plants  and  in  the  embryos  of  seeds. 

Minerals. — In  addition  to  the  foregoing  groups  of  substances, 
which  are  all  organic,  the  bird 's  body  also  contains  inorganic  material. 
Included  in  this  are  the  minerals,  which  are  to  be  found  not  only  in  the 
skeleton  but,  in  smaller  proportions,  in  all  organs,  tissues,  and  fluids 
of  the  bird's  body.  It  is  evident  that  growing  birds  need  a  constant 
supply  of  minerals  so  that  they  may  be  enabled  to  form  new  bone  and 
other  mineral-containing  tissue.  Just  as  evident  is  the  necessity  of 
providing  laying  birds  with  the  essential  minerals  for  egg-shell  forma- 


14  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

tion.  Experience  has,  moreover,  proved  the  necessity  of  supplying  all 
kinds  of  adult  birds  with  minerals,  because  their  tissues  are  subject  to 
general  wear  and  tear,  and  must  be  renewed. 

The  parts  played  in  metabolism  by  the  various  minerals  are  little 
known.  Calcium,  magnesium,  and  phosphorus  are  needed  for  bone 
formation,  calcium  also  for  shell  formation.  Calcium  in  addition  is 
an  important  constituent  of  the  blood,  giving  to  this  fluid  its  ability 
to  coagulate  (clot).  Calcium  is  also  a  constituent  of  the  white  of  egg 
and  of  the  phosphates  of  egg  yolk.  Sodium  chloride  is  also  needed  by 
all  plant  eating  animals  for  the  elimination  of  the  excess  potassium 
contained  in  the  feed.  Chlorides  of  sodium  and  potassium  are  needed 
as  constituents  of  the  body  fluids  and  tissues.  Iodine  is  required  in 
small  quantities,  and  is  found  in  the  thyroid  gland.  Sulphur  and 
silicon  are  constituents  of  the  feathers.  Iron  appears  in  eggs  and  also 
is  an  important  constituent  of  the  haemoglobin  which  gives  to  the 
blood  its  power  to  carry  oxygen.  Besides  these,  copper,  zinc,  and 
arsenic  are  found  in  small  quantities.  The  requirements  are  small 
because  the  body  waste  is  inconsiderable. 

Besides  acting  as  building  material  for  the  body,  the  minerals  aid 
in  the  digestion,  absorption,  distribution,  and  excretion  processes. 
It  is  an  interesting  fact  that  birds  can  stand  starvation  with  regard 
to  the  organic  nutrients,  which  are  commonly  considered  to  be  the 
most  important,  longer  than  they  can  stand  mineral  starvation.  As 
each  particular  mineral  has  one  or  more  specific  functions  in  the 
organism,  a  deficiency  results  in  disease.  Toe  picking  is,  in  some  cases 
at  least,  such  a  disease  and  is  paralleled  by  the  condition  of  horn  eating 
occurring  in  cattle  in  South  Africa.  Rickets,  caused  by  lack  of  lime, 
has  already  been  dealt  with  under  vitamin  D,  the  factor  controlling  the 
deposition  of  that  mineral.  Lack  of  iron  causes  anemia.  Too  little 
iodine  also  causes  ill  effects  in  poultry,  as  in  mammals,  where  it  results 
in  certain  types  of  goiter. 

Although  the  organic  nutrients,  when  fed  in  excess,  are  stored, 
such  is  not  the  case  with  minerals.  Whatever  is  not  needed  by  the 
body  is  immediately  disposed  of  through  excretion.  It  is  evident, 
therefore,  that  their  supply  in  the  food  must  be  continuous. 

Water. — Water  as  a  nutrient  is  of  the  utmost  importance  to  the 
body.  Besides  being  an  important  structural  component,  water  is  a 
necessary  agent  in  practically  all  body  processes  which  are  chemical 
reactions  between  dissolved  substances  with  water  as  the  solvent. 

The  fowl's  body  is  continuously  losing  moisture  through  the 
expired  air  and  the  excretions.  Laying  birds  lose  additional  moisture 
through  the  eggs.     Therefore  water  must  be  provided  continuously. 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE 


15 


The  water  formed  in  the  body  by  oxidation  of  organic  nutrients  does 
not  cover  more  than  a  small  fraction  of  the  actual  needs.  With 
increasing  environmental  temperature  the  needs  for  water  are  cor- 
respondingly increased,  because  of  increased  loss  of  water  through  the 
lungs.  This  increased  evaporation  of  water  through  the  lungs 
apparently  is  the  bird's  only  means  of  temperature  regulation.  Most 
of  the  common  mammals  possess  a  further  mechanism  for  heat  regula- 
tion in  the  sweat  glands,  which  is  probably  the  explanation  of  the 
commonly  observed  fact  that  they  are  better  able  to  withstand  high 
temperatures  than  birds. 

FEEDS   AS   COMBINATIONS   OF    NUTRIENTS 

During  the  previous  discussion  the  nutrients  have  been  considered 
as  pure  and  well  defined  substances,  which  can  be  accurately  identified 
by  chemical  or  biological  examination.  This  was  to  explain  clearly 
their  individual  characteristics  and  behavior. 

In  practical  feeding,  however,  it  is  not  the  separate  nutrients  which 
are  dealt  with,  but  feedstuffs  which  are  mixtures  of  them.  Neither 
are  the  nutrients  present  in  pure  form,  but  as  so-called  crude  proteins, 
crude  fats,  etc.  The  fact  that  the  nutrients  are  present  in  a  mixture 
does  not  affect  the  underlying  principles  of  nutrition,  which  govern 
each  one  of  them  separately.  Of  much  more  concern  is  the  form  in 
wrhich  they  are  present.  This  is  of  primary  importance  with  proteins, 
carbohydrates,  and  fats. 

TABLE   1 
The  Per  Cent  Composition  of  Feedstuffs  Used  in  Digestibility  Trials  with 

Poultry 


Feedstuff 


Barley 

Corn 

Fish  meal 

Meat  scrap 

Potatoes 

Rice,  unpolished 

Rice  bran 

Rye 

Soybean  meal 

Wheat 

Wheat  bran 

Yeast 


Moisture 

Minerals 

Organic 
substance 

Crude 
protein 

Nitrogen- 
free 
extract 

Crude 

fat 

12.33 

2.88 

84.79 

13.93 

64.16 

1.80 

13.00 

1.30 

85.70 

9.90 

69.20 

4.40 

9.89 

12.30 

77.81 

61.93 

2.57 

13.31 

9.32 

17. 15 

73.53 

50.24 

2.21 

16.15 

74.69 

1.39 

23.92 

1.84 

21.23 

0.10 

11.65 

1.72 

86.63 

10.45 

73.52 

1.93 

11.05 

11.43 

77.52 

14.13 

35.96 

19.31 

15.32 

1.98 

82.70 

9.83 

69.02 

1.65 

10.79 

6.21 

83.00 

42.68 

28.76 

7.23 

13.42 

1.92 

84.66 

14.03 

66.47 

1.93 

12.40 

5.41 

82.19 

14.87 

54.25 

4.06 

8.73 

6.66 

84.61 

55.44 

26.44 

2.73 

Crude 
fiber 


4.90 
2.20 

4.93 
0.75 
0.73 
8.12 
2.20 
4.33 
2.23 
9.01 
0.50 


16 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE   2 

Digestibility  Coefficients  for  the  Different  Nutrients  of  Common 
Feed-stuffs  for  Poultry* 


Feedstuff 


Barley 

Corn 

Fish  meal 

Meat  scrap 

Potatoes 

Rice,  unpolished. 

Rice  bran 

Rye 

Soybean  meal 

Wheat 

Wheat  bran 

Yeast 


Organic 
substance 


75.4 
86.2 
88.9 
76.6 
78.3 
78.0 
59.7 
79.2 
76.6 
84.3 
55.3 
75.5 


Crudo 
protein 


75.1 

58.  Of 

90.6 

73.6 

46.9 

76.9 

66.9 

63.0 

83.4 

78.9 

64.3 

76.2 


Nitrogen-free 

extract 

(carbohydrates) 

Fat 

82.2 

48.0 

93.0 

8.53 

98.2 

82.1 

84.5 

88.1 

64.1 

58.2 

87.7 

85.6 

28.5 

75.3 

84.1 

89.3 

39.8 

61.2 

55.6 

82.8 

57.1 

Crude 
fiber 


*  Figures  in  this,  the  preceding  and  the  followiug  table  mainly  from  Katayama  (1924)  supplemented 
from  Voltz  (1909  and  1923). 

t  This  figure  was  obtained  by  a  different  method  which  possibly  gives  a  somewhat  low  value. 

TABLE  3 

Pounds  of  Nutrients  Digestible  to  Poultry  in  100  Pounds  of  Feed  (Based 
on  Composition  of  Feeds  as  Given  in  Table  1) 


Feedstuff 


Barley 

Corn 

Fish  meal 

Meat  scrap 

Potatoes 

Rice,  unpolished 

Rice  bran 

Rye 

Soybean  meal 

Wheat 

Wheat  bran 

Yeast 


Organic 
substance 


63.93 
73.87 
69.17 
53.03 
18.73 
74.05 
46.28 
65.50 
63.58 
71.37 
45.45 
63.88 


Protein 


10.46 

5.74 

56.11 

36.98 

0.86 

8.04 

9.45 

6.19 

35.61 

11.07 

9.56 

42.25 


Nitrogen-free 

extract 

(carbohydrates) 


52.74 

64.38 

None 

(2.21) 

17.94 

64.77 

20.93 

59.08 

21.65 

59.36 

33.20 

21.89 


Fat 


0.86 

3.75 
13.07 
13.24 


1.24 
16.93 
0.47 
6.08 
0.77 
2.26 
1.56 


The  proportions  in  which  these  nutrients  are  present  can  be  accurately 
determined  by  analysis.  Tables  of  the  composition  of  feedstuffs  give 
the  average  proportion  of  these  classes  of  nutrients  in  the  common 
feeds. 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE 


17 


Digestibility. — Although  analyses  of  composition  are  of  great 
importance,  of  still  greater  importance  to  the  practical  feeder  is  the 
digestibility  of  the  feed.  Such  information  can  be  obtained  only  by 
actual  feeding  tests  under  carefully  controlled  laboratory  conditions. 

In  these  tests  definite  amounts  of  an  analyzed  food  are  given  to 
an  animal  and  the  corresponding  excretions  are  analyzed.  The 
nutrients  fed  and  not  excreted  in  the  feces  are  accepted  as  the  actually 
digested  food.  In  this  way,  therefore,  the  digestible  matter  is  deter- 
mined, which  again  makes  possible  the  computation  of  the  digestibility 
coefficients.  These  give  the  number  of  parts  digested,  that  is,  the  parts 
available  to  the  body,  of  each  100  parts  of  the  particular  nutrient  fed. 

Example:  Katayama  (1924)  found  as  the  average  of  three  experi- 
ments with  wheat  bran  fed  to  poultry,  the  following  digestibility 
coefficients : 


Organic 
substance 

Protein 

Carbohydrates 

Fat 

Crude  fiber 

55.3 

64.3 

61.2 

55.6 

-    0 

These  figures  simply  mean  that  of  each  100  parts  of  organic  substance 
(gross  weight  of  every  feed  less  moisture  and  mineral  content)  in 
wheat  bran  fed  to  poultry,  44.7  parts  by  weight  were  regained  from 
the  feces  i.e.,  wasted).  Consequently  only  the  remaining  55.3  parts 
were  retained  by  the  body,  that  is  to  say,  digested.  Therefore  the 
digestibility  coefficient  of  the  organic  substance  of  wheat  bran  for 
poultry  is  55.3.  It  is  low  because  of  the  large  amount  of  crude  fiber 
and  pentosans  it  contains.  The  corresponding  figure  for  the  protein 
part  of  bran  was  64.3 ;  carbohydrates  61.2 ;  and  fats  55.6. 

For  the  sake  of  convenience  in  compounding  rations,  tables  are 
general^  given  for  the  pounds  of  digestible  nutrients  in  100  pounds 
of  feed.  These  figures  are  computed  from  the  composition  and  diges- 
tibility coefficients.  The  composition  of  the  wheat  bran  used  in  the 
experiments  was  as  follows : 


Pounds  in  100  pounds  of  wheat  bran 

Component 

Total 

Digestible 

Moisture 

12.40 

5.41 

82.19 

14.87 

54.25 

4.06 

9.01 

Mineral  (also  called  ash) 

Organic  substance 

45.44 

Proteins 

9  56 

Carbohydrates 

Fats 

33.20 
2  26 

Crude  fiber 

0  00 

Total 

100.00 

45.44 

18  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

That  is,  100  pounds  of  bran  contained.  82.19  pounds  of  organic  sub- 
stance ;  and  this  organic  substance  was  made  up  of  14.87  pounds  of 
protein,  54.25  pounds  of  carbohydrates,  4.06  pounds  of  fat  and  9.01 
pounds  of  crude  fiber.    The  digestible  organic  nutrients  in  100  pounds 

55  3 
of  bran,  therefore,  were  82.19  X        *     =45.44  pounds.     Correspond- 

64  3 
ing  figures  for  protein  are  given  by  14.87  X  -77^:  ;  for  carbohydrates, 

61 2  55  6 

54.25  X  -j^ ;  and  for  fat,  4.06  X  -tttx  ;  crude  fiber,  0.  As  a  result  the 

following  are  obtained : 

Pounds  of  Digestible  Nutrients  in  100  Pounds  of  Wheat  Bran 


Organic 
substance 

Protein 

Carbohydrates 

Fats 

Proteins+ 
carbohydrates 

+fats 

45.44 

9.56 

33.20 

2.26 

45.02 

The  sum  of  digestible  proteins,  carbohydrates,  and  fat  should  always 
be  equal  to  the  digestible  organic  substance.  Because  of  unavoidable 
experimental  errors,  there  are  always  slight  discrepancies.  In  this 
case  the  discrepancy,  as  will  be  noted,  amounted  to  0.42  pounds. 

Since  different  kinds  of  animals  have  marked  differences  in  their 
digestive  systems,  the  digestibility  will  vary  for  different  species  and 
has  to  be  specially  determined  for  each  species  (i.e.,  for  cattle,  horses, 
hogs,  chickens,  etc.).  Because  of  the  experimental  difficulties,  caused 
by  the  combined  excretions  of  feces  and  urine,  work  with  chickens 
has  been  carried  out  only  on  a  very  limited  scale.  Outside  of  the  few 
coefficients  given  in  table  2,  figures  have  to  be  accepted  with  the 
greatest  caution.  Digestibility  coefficients  obtained  in  experiments 
with  other  kinds  of  animals,  even  with  other  species  of  poultry,  posi- 
tively cannot  be  applied  to  chickens ;  they  are  very  misleading.  No 
complete  fundamental  standards  being  available,  feeding  of  poultry 
has  to  be  based  more  or  less  on  practical  experience,  and  knowledge 
of  the  composition  of  the  feeds. 

Nutritive  Ratio. — Even  when  the  digestibility  coefficients  are 
known  it  is  not  possible  to  arrange  feeding  standards,  without  taking 
into  consideration  the  balance  between  the  different  organic  nutrients 
(excepting  the  vitamins).  This  is  called  the  nutritive  ratio  and  gives 
the  ratio  between  digestible  proteins  on  the  one  hand  and  digestible 
carbohydrates  and  fats  on  the  other.  To  put  it  in  other  words,  the 
nutritive  ratio  gives,  for  a  particular  feed  or  combination  of  feeds, 
the  proportions  of  available  body  building  material,  the  proteins,  as 
opposed  to  the  available  energy  and  heat  sources,  carbohydrates  and 
fats. 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE 


19 


In  the  given  case  of  wheat  bran  the  nutritive  ratio  for  poultry 
expresses  the  ratio  of  the  digestible  proteins  (9.56)  to  the  sum  of  the 
digestible  carbohydrates  (33.20)  plus  2^4  times  the  digestible  fats 
(2.26)  in  100  pounds  of  bran,  that  is  9.56  to  (33.20  +  5.08),  which  on 
reduction  to  simplest  terms  gives  one  part  of  protein  to  four  parts  of 
the  rest  of  the  ration  (usually  written  1:4.0). 

In  the  case  of  combinations  of  feeds  the  actual  digestible  amounts 
of  the  different  nutrients  are  found  by  addition.     Example : 


Pounds  of  digestible  nutrients* 

Composition  of  mash 

Proteins 

Carbohydrates 

Fats 

26.67  pounds  ground  wheat 

2.95 

2.79 
1.53 

7.4 

15.83 

14.07 

17.17 

0.44 

0.21 

26.67  pounds  ground  barley 

0.23 

26.67  pounds  yellow  corn 

20.00  pounds  meat  scrap 

1.00 
2.60 

Total 

14.67 

47.51 

4.04 

14. 67  :  47. 51  +  (2^X4. 04)  =  14.  67  :  56. 60  =  1  : 3. 86. 


*  Digestible  nutrients  in  100  pounds  of  each  feed  taken  from  table  3  and  reduced  to  corresponding 
figure  for  amount  of  each  feed  in  100  pounds  of  mash. 

Proteins  cannot  be  compared  with  substances  as  different  as  carbo- 
hydrates and  fats,  without  being  translated  into  the  same  terms.  The 
characteristic  common  to  all  three  groups  of  nutrients  is,  that  under 
certain  conditions  they  burn  and  yield  heat.  The  unit  of  heat  is  the 
Calorie  ;4  the  nutritive  ratio  therefore  expresses  the  number  of  Calories 
(that  is,  the  amount  of  heat)  derived  from  proteins  as  compared  with 
the  Calories  derived  from  carbohydrates  and  fats.  Proteins  and  carbo- 
hydrates give  practically  the  same  heat  on  complete  oxidation  in  the 
body  (about  1860  calories  to  a  pound)  ;  fats,  however,  give,  as  already 
explained,  two  and  one-fourth  times  as  much  heat  (about  4200  to  a 
pound) .  The  nutritive  ratio  of  a  food,  therefore,  is  properly  expressed 
as  proteins  to  carbohydrates  +  2%  times  fats.  The  nutritive  ratio  is 
also  frequently  computed  from  "the  total  digestible  nutrients"5  and 
is  thus  expressed  as  proteins  to  total  digestible  nutrients  minus  pro- 
teins. These  two  ways  of  computing  should  give  the  same  result  for 
a  given  ration. 


*  A  Calorie  (with  the  capital  C)  is  the  energy  which  (in  terms  of  heat)  is 
required  to  raise  the  temperature  of  1  kilo  of  water  1°  Centigrade  or  1  pound  of 
water  4°   Fahrenheit  and  equals  1000  calories   (small  c). 

5  ' '  Total  digestible  nutrients ' '  is  used  by  some  authorities  to  mean  the  diges- 
tible organic  substance  in  100  pounds  of  feed,  when  allowance  is  made  for  the 
higher  energy  content  of  fat.  It  is  equal  to  protein  +  carbohydrates  +  2^  fat. 
In  the  given  case  of  wheat  bran  "the  total  digestible  nutrients' '  are  therefore 
47.85  pounds  as  compared  with  45.44  pounds  of  digestible  organic  substances. 


20  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  proper  nutritive  ratio  has  to  be  determined  experimentally. 
It  will  vary  with  the  different  purposes  for  which  the  feeding  is  done, 
as,  for  example,  growth,  fattening,  or  egg  production.  The  processes 
of  growth  and  egg  production  naturally  require  more  of  the  tissue- 
forming  material,  proteins,  than  the  process  of  fattening.  Not  know- 
ing the  digestibility  of  the  different  feeds,  it  is,  of  course,  not  possible 
to  determine  nutritive  ratios  with  any  degree  of  exactness.  It  has 
been  assumed,  however,  that  growth  and  egg  production  require  ratios 
between  1  A  and  1 :6,  which  may  be  called  narrow  ratios.  Fattening, 
on  the  other  hand,  requires  more  of  the  heat  and  fat-forming  nutrients, 
the  optimum  ratios  ranging  between  1 :6  and  1 :8,  and  these  are  called 
wide  ratios. 

The  fact  that  the  digestible  part,  of  the  food  has  to  be  specially 
determined,  indicates  that  not  all  of  a  food  is  digestible.  A  part, 
varying  greatly  with  the  different  kinds  of  food,  is  not  digested  and  is 
passed  out  with  the  droppings.  A  large  part  of  the  undigested  food 
in  poultry  is  always  the  crude  fiber,  which  as  cellulose  makes  up  as 
much  as  30  per  cent  of  the  walls  of  the  cells  of  which  the  grains  are 
composed.  Neither  are  certain  carbohydrates,  the  pentosans,  digested 
to  any  considerable  degree.  These  are  present  in  appreciable  per- 
centages in  the  common  grains,  comprising  about  7  per  cent  of  corn, 
6.5  per  cent  of  wheat  and  as  much  as  25  per  cent  of  wheat  bran. 

It  has  been  demonstrated  that  birds  cannot  exist  on  pure  digestible 
nutrients  alone,  but  that  addition  of  bulk  in  the  form  of  crude  fiber 
is  needed  to  maintain  them  in  good  condition.  The  explanation  of 
this  phenomenon  is  not  known,  but  it  is  assumed  that  the  rough  fiber 
acts  as  an  irritant  stimulating  the  secretion  of  digestive  juices  and  the 
peristaltic  movement  of  the  intestines.  There  is  no  evidence  in  sup- 
port of  the  prevalent  opinion  that  the  presence  of  bulk  is  of  any  assist- 
ance in  "opening  up"  the  rest  of  the  food  to  digestion.  All  poultry 
rations  furnish  more  or  less  bulk,  a  large  part  of  it  in  the  form  of 
crude  fiber.  The  amount  of  bulk  giving  the  best  results  has  not  yet 
been  definitely  determined.  It  appears  as  if  there  is  rather  a  large 
margin  of  safety  within  which  variations  do  not  seem  to  make  much 
difference.  Thus  certain  rations  with  as  little  as  2  per  cent  and  others 
with  as  much  as  10  per  cent  crude  fiber  have  given  good  results.  Most 
common  rations,  with  6  per  cent  crude  fiber,  have  more  than  6  per  cent 
of  bulk  because  of  other  indigestible  matter.  The  bulk  may  be  as 
high  as  30  per  cent,  which  is  certainly  more  than  is  desirable. 

Not  all  of  the  digested  and  absorbed  food,  however,  is  available  to 
the  body  as  energy.  In  particular,  the  proteins  are  not  broken  down 
completely ;  parts  which  are  still  able  to  combine  with  oxygen,  yielding 


Bul.  417 


POULTRY    FEEDING  :    PRINCIPLES    AND    PRACTICE 


21 


heat,  are  always  excreted  through  the  kidneys  as  uric  acid  and  urea. 
Thus  energy  is  lost  as  far  as  the  bird's  body  is  concerned. 

The  digestion  of  food  requires  energy,  which  must  also  be  sub- 
tracted from  the  food  energy,  in  order  that  the  amount  actually  avail- 
able to  the  bird  for  other  purposes  may  be  known.  The  digestive  work, 
of  course,  varies  with  the  different  foods,  the  digestion  of  animal 
products  naturally  being  easier  than  the  digestion  of  fibrous  vegetable 
products.  Therefore  the  available  or  net  energy  of  feeds  is  denned  as 
the  food  energy  less  the  sum  of  remaining  energy  in  the  excretions  and 
the  energjr  required  for  digestive  work. 

By  measuring  the  loss  of  heat  and  the  respiratory  gases  from  the 
bird's  body  under  the  different  conditions  of  starvation,  maintenance, 
and  production,  the  energy  requirements  (or  actual  food  needs)  of 
the  bird  have  been  determined.  The  requirements  are  directly  cor- 
related with  the  surface  area  of  the  body.  Feed  requirements  there- 
fore vary  with  the  size  of  the  bird,  since  the  smaller  body  always  has 
a  greater  surface  in  proportion  to  body  weight.  In  spite  of  frequently 
made  statements  to  the  contrary,  the  actual  energy  requirements  of 
poultry  (not  laying)  do  not  exceed  those  of  other  farm  animals  or 
humans  on  the  basis  of  body  surface.  On  the  basis  of  a  given  unit  of 
weight  the  requirements  of  an  animal  increase  with  decreasing  size, 
as  will  be  seen  from  table  4. 

TABLE  4 

Comparative  Energy  Requirements  for  Man  and  Some  Farm  Animals 

(Data  from  Ellenberger  imd  Scheunert,  1925,  and  Gerhartz,  1914) 


Kind  of  animal 


Horse 

Hog 

Human 

Dog 

Goose,  young 

Domestic  fowl,  non-laying. 


Body  weight 
in  pounds 


970 

282 

141 

33 

7. 


4.4 


Energy  requirements  per  24 
hours  in  calories 


Per  pound 
body  weight 


5.1 
8.7 
14.6 
23.4 
30.3 
38.7 


Per  square 

meter  surface 

area 


948 
1078 
1042 
1039 

967 
1020 


Energy  requirements  during  molt  and  broodiness  are  practically  the 
same  as  under  ordinary  non-laying  conditions. 

The  laying  process,  involving  the  formation  of  eggs,  however, 
requires  approximately  80  per  cent  more  energy  than  simple  main- 
tenance, which  is  four  times  as  much  energy  as  is  required  for  the 


22  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

formation  of  an  equivalent  amount  of  body  fat  in  hogs.  Egg  pro- 
duction as  an  industry,  therefore,  is  badly  handicapped  as  compared 
with  the  fattening  of  cattle  or  hogs,  and  it  is  evident  that  great  care 
should  be  taken  to  supply  both  the  most  efficient  and  cheapest  feed  to 
poultry. 

Comparison  of  Quality  of  Nutrients  in  Different  Feeds. — Not 
expressed  in  the  digestibility  coefficient  and  the  nutritive  ratio,  but 
just  as  important  if  not  more  so,  is  the  quality  of  the  food  protein. 
There  is  no  fundamental  difference  between  animal  and  vegetable  pro- 
teins, provided  these  latter  contain  the  essential  amino  acids.  There 
is,  however,  a  difference  between  the  efficiency  of  the  two,  because  the 
vegetable  cell  membrane,  being  composed  largely  of  non-digestible 
cellulose  (crude  fiber),  hinders  digestion  of  the  included  proteins,  so 
that  more  energy  is  required  for  their  digestion.  Even  considering 
this,  there  is  frequently  sufficient  difference  in  price  to  justify  a  more 
extensive  use  of  the  vegetable  protein  concentrates. 

Another  point  to  consider  is  that,  as  indicated  before,  many  of 
the  grain  proteins  are  lacking  in  one  or  more  of  the  essential  amino 
acids.  This  deficiency  is  not  the  same  in  all  of  them,  so  that  perfectly 
well  balanced  proteins  might  be  obtained  by  making  the  proper  selec- 
tion of  grains  alone.  This  is  more  practically  accomplished,  however, 
by  introducing  suitable  protein  concentrates,  such  as  fish  scrap,  meat 
scrap,  soybean  meal,  peanut  meal,  etc.,  as  supplements  to  the  grains. 

Although  the  question  of  quality  is  thus  of  great  importance  in 
the  case  of  proteins,  with  carbohydrates  all  digestible  carbohydrates 
are  equivalent.  The  digestible  carbohydrates  consist  largely  of  starch. 
Organic  acids  like  lactic  acid  and  tartartic  acid  and  also  alcohols  in 
the  feed  are  generally  counted  as  carbohydrates,  since  they  have  prac- 
tically the  same  energy  content  as  sugars  and  are  used  by  the  body  like 
the  other  members  of  the  group.  Sometimes,  however,  this  whole 
group  is  called  "nitrogen-free  extract."  This  is  because  "carbo- 
hydrates" in  the  strict  sense  of  the  term,  do  not  include  these  acids 
and  alcohols. 

The  fats  of  animal  feeds  are  more  easily  digested  by  birds  than 
those  of  vegetable  feeds.  This  difference  is  not  caused  by  any  differ- 
ence in  composition  but  is  due  to  the  fact  that  vegetable  fats  generally 
are  less  accessible  to  the  digestive  juices  because  contained  in  cells  with 
cellulose  walls. 

Vitamins  practically  always  originate  from  plants,  but  whether 
they  are  supplied  from  vegetable  or  animal  products  is  immaterial,  as 
far  as  known.  Nothing  is  known  about  their  digestibility,  their 
chemical  composition  not  having  been  ascertained  as  yet.    Their  defini- 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE  23 

tion  really  is  based  on  the  utilized  part  of  them,  since  their  presence 
and  potency  are  judged  wholly  by  their  physiological  effects.  Of  the 
vitamins,  vitamin  C  does  not  have  to  be  provided  in  the  feed  and  the 
vitamins  B  and  E  are  widely  distributed  in  the  ordinary  poultry  feeds, 
so  that  no  special  attention  has  to  be  paid  to  them  to  ensure  an  ade- 
quate supply.  With  regard  to  the  two  remaining  vitamins,  care  has 
to  be  taken  that  the  bird's  needs  are  met.  Excessive  feeding  of  the 
vitamins  discussed  in  this  bulletin,  however,  has  never  been  demon- 
strated to  do  any  good. 

There  is  no  way  of  testing  the  digestibility  of  minerals.  In  order 
to  determine  definitely  whether  they  are  supplied  in  sufficient  amounts, 
it  is  necessary  to  determine  what  is  called  the  mineral  balance.  If 
more  of  a  mineral  is  taken  in  with  the  food  than  is  passed  out  in  the 
combined  excretions  and  eggs,  the  bird  is  said  to  be  in  a  positive 
balance;  the  reverse  illustrates  a  negative  balance.  The  effort  is 
always  made  to  feed  at  least  enough  minerals  to  get  the  intake  as  high 
as  the  outgo.  In  growing  birds  the  intake  must  be  higher  than  the 
outgo  to  allow  for  bone  and  tissue  formation. 

With  the  exception  of  calcium,  phosphorus,  sodium,  and  possibly 
chlorine,  the  minerals  are  found  in  sufficient  amounts  in  ordinary 
feeds.  The  quantities  present  are  always  small,  but  the  needs  are 
slight,  so  that  special  attention  generally  need  be  given  only  to  the 
supply  of  the  four  elements  just  mentioned. 

Although  these  four  elements  can  be  supplied  in  inorganic  form, 
such  as  limestone,  phosphates,  and  common  salt,  or  tied  up  with 
organic  matter,  one  element,  sulphur,  behaves  differently.  It  has  to 
be  supplied  in  a  particular  form.  This  element  cannot  be  used  in  the 
pure  form  by  birds,  but  must  be  provided  in  certain  proteins  in  which 
it  appears  as  a  constituent  of  the  amino  acid  called  cystine. 


POULTRY  FEEDING  PRACTICE 

GENERAL   COMPOSITION   OF   A   POULTRY   RATION 

The  common  fowl  is  by  nature  a  grain  and  insect  eater,  wherefore 
poultry  feeding  properly  is  based  on  grains  as  the  main  supply  of 
nourishment.  Such  grains  should  be  used  in  composing  a  poultry 
ration  as  are  available  at  a  reasonable  cost,  because  the  main  nutrient 
group  contained,  namely,  the  carbohydrates,  is  the  same,  whether 
obtained  from  one  grain  or  another.  Consequently  there  is  no  "best" 
grain  for  poultry. 


24  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Grain  prices  always  fluctuate,  and  they  fluctuate  unevenly  for  the 
different  kinds  of  grain.  Grain  prices  also  depend  upon  locality,  the 
locally  grown  grains  usually  being  cheaper  than  those  imported  from 
other  districts.  Since  one  grain  is  practically  as  good  as  any  other, 
poultry  rations  often  vary,  and  always  should  vary  according  to  local 
prices  and  market  conditions.  This  explains  the  fact  that  poultry- 
men  in  wheat  districts  use  wheat  as  the  base  of  their  poultry  feeds, 
while  those  in  the  corn  districts  use  corn.  Since  in  California  barley 
ordinarily  is  the  cheapest  grain,  barley  should  here  have  a  conspicuous 
place  in  any  feed  formula. 

Although  grains  are  the  base  of  the  feed,  they  are  not  under 
ordinary  conditions  a  complete  feed  for  poultry  kept  for  commercial 
purposes.  The  proteins  of  common  grains  are  inadequate  as  to  kinds 
and  amounts.  The  grains  are  further  deficient  in  certain  minerals, 
certain  vitamins,  and  in  water.  It  is  therefore  altogether  essential  that 
the  grain  ration  for  birds  be  supplemented  with  water,  vitamins,  pro- 
teins, and  minerals.  Because  the  protein  concentrates  are  usually 
available  in  the  form  of  meals  or  scraps,  which  cannot  easily  be  fed 
in  a  mixture  with  the  whole  grains,  it  is  customary  to  divide  the 
poultry  ration  into  two  parts  by  supplying  the  supplements  in  the 
form  of  a  mash. 

For  the  sake  of  convenience  it  is  common  practice  to  compose  the 
mash  in  such  a  way  as  to  make  the  proportions  of  the  different 
nutrients  about  right  when  grains  and  mash  are  fed  in  equal  amounts. 
In  such  case  it  is  always  necessary  to  add  to  the  concentrates  a  certain 
amount  of  ground  grains  and  possibly  grain  by-products  in  order  to 
maintain  the  proper  nutritive  ratio. 

It  is  convenient  also  to  include  suitable  mineral  concentrates  in  the 
mash.  This  is  in  order  to  ensure  at  all  times  consumption  of  the  right 
kinds  and  amounts  of  minerals  for  growth  and  egg  production.  Water 
and  certain  vitamin  supplements  are  commonly  fed  separately. 

GRAINS 

The  exact  combination  of  grains  is  of  slight  importance.  The 
separate  kinds,  and  also  the  proportions  of  each  kind,  to  be  used  at  a 
time  will  depend  largely  upon  price  conditions. 

A  variety  of  grains  is  always  preferable,  because  it  increases  the 
palatability  and  therefore  also  increases  food  consumption.  A  variety 
is,  on  the  other  hand,  by  no  means  necessary.  Birds  have  repeatedly 
been  raised  and  kept  in  good  production  by  using  one  grain  only 
when  it  was  properly  supplemented. 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE  25 

Barley. — Barley  is  an  excellent  feed  for  poultry,  particularly  when 
the  price  is  considered.  The  only  limitation  to  the  feeding  of  barley 
may  be  the  comparatively  low  palatability.  Birds  raised  on  other 
grains  do  not  take  to  barley  readily,  but  if  they  have  been  trained  to 
eat  it  early  enough  they  like  it  and  eat  about  as  much  of  it  as  they 
would  of  any  other  grain.  Whole  barley  can  be  fed  to  birds  as  early 
as  six  weeks  of  age.  In  large  sections  of  Europe,  barley  is  fed  as  the 
only  grain,  and  the  results  are  very  satisfactory.  In  order  to  train 
adult  birds  to  eat  this  grain  or  in  order  to  make  them  eat  more  of  it, 
it  is  a  common  practice  to  soak  or  "process"  it  (letting  it  germinate 
and  develop  root  sprouts).  Hulled  barley  has  no  advantage  over  the 
whole  grain  and  may  moreover  be  less  palatable.  The  higher  price 
therefore  is  not  justified,  particularly  as  a  poor  grade  grain  is  often 
used  in  the  manufacture.  The  digestible  nutrient  content  of  barley 
is  about  64  pounds  to  100  pounds  of  grain;  it  should  weigh  at  least 
42  pounds  to  the  bushel. 

Corn. — Yellow  corn  is  a  most  valuable  grain  for  poultry,  being 
highly  palatable,  highly  digestible,  and  generally  also  reasonable  in 
cost.  Figures  of  different  observers  do  not  exactly  agree,  but  it  is 
known  that  100  pounds  of  corn  contain  at  least  73  pounds  of  digestible 
nutrients. 

In  Roumania,  a  corn  producing  country  of  Europe,  it  is  a  common 
experience  that  stored  corn  is  to  be  preferred  to  new  corn  in  feeding. 
In  trials  with  poultry,  Nitzescu  (1918)  found  that  corn  a  year  old 
was  better  utilized  and  contained  over  three  pounds  more  of  digestible 
nutrients  to  a  hundred  than  new  corn. 

Yellow  corn  differs  from  white  corn  and  most  other  grains  in  that 
it  contains  vitamin  A.  The  amounts,  however,  are  rather  small,  2% 
ounces  of  yellow  corn  per  adult  bird  a  day  being  needed  in  order  to 
prevent  nutritional  disease  (see  p.  11). 

Yellow  corn  also  contains  the  pigment  (xanthophyll)  which  gives 
yellow  color  to  the  skin  and  shanks  of  the  bird  and  to  the  egg  yolk. 
There  is  not  enough  of  this  pigment,  however,  to  make  it  an  unde- 
sirable poultry  feed,  even  when  fed  in  large  amounts. 

As  a  matter  of  fact,  yellow  corn  is  such  a  desirable  grain  that  it 
perhaps  always  should  be  a  part  of  the  poultry  ration.  There  is  no 
advantage  in  feeding  the  grain  in  cracked  form  to  adult  birds ;  on  the 
contrary,  certain  valuable  parts  of  the  corn  are  usually  lost  in  the 
cracking  process. 

White  corn  is  presumably  just  as  digestible,  but  possibly  not  quite 
as  palatable  for  poultry  as  the  yellow  variety.  It  does  not  contain 
vitamin  A. 


26  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Oats. — Heavy  oats  are  another  desirable  poultry  grain.  Light  oats 
(i.e.,  weighing  less  than  36  pounds  to  the  bushel),  since  they  contain 
much  more  undigestible  fiber,  are  of  low  value.  Hulled  oats  have  no 
advantage  over  whole  oats  as  feed  for  adult  birds,  but  do  have  an 
advantage  of  lower  price  over  steel  cut  oats  as  feed  for  young  stock. 
The  digestibility  of  oats  has  not  been  fully  determined.  It  is  probably 
slightly  lower  than  that  of  barley  because  of  the  pentosan  content,  the 
crude  fiber  content  being  practically  the  same. 

Wheat. — Wheat  is  also  eaten  very  readily  by  birds,  in  fact  so 
eagerly  that  it  has  for  a  long  time  been  looked  upon  as  essential  in 
poultry  feeding.  As  was  shown  during  the  late  war,  it  is  not  at  all 
indispensable,  and  the  high  price,  as  compared  with  other  grains, 
should  doubtless  make  it  much  less  popular  than  it  is  at  the  present 
time.  Wheat  contains  about  72  pounds  of  digestible  nutrients  to  the 
hundred. 

Other  Grains. — Feterita,  kafir,  millet,  milo,  rice,  and  other  grains 
can  likewise  be  fed  successfully  to  poultry,  kafir  perhaps  being  the 
most  palatable.  Rice  is  now  being  produced  in  California  in  steadily 
increasing  amounts.  While  the  superior  grades  are  far  too  expensive 
for  use  in  poultry  feeding,  offals,  such  as  cracked  rice,  and  by- 
products, such  as  bran  and  rice  polish,  can  be  obtained  at  very  reason- 
able prices  and  represent  very  desirable  poultry  feeds,  provided  the 
products  are  of  standard  good  quality. 

Summary  of  the  Feeding  Value  of  Grains. — Grains  primarily  sup- 
ply carbohydrates,  but  at  the  same  time  also  provide  some  of  all  other 
nutrients.  Apart  from  the  slight  vitamin  A  content  of  yellow  corn, 
there  is,  as  pointed  out,  little  qualitative  difference  between  the  differ- 
ent grains  with  regard  to  vitamins.  Therefore  their  total  digestible 
nutrients  give  a  fair  expression  of  their  relative  feeding  value.  Com- 
paring the  digestible  nutrients  (see  table  3)  and  not  considering  the 
value  of  variety,  it  is  seen  that  corn  is  slightly  higher  in  feeding  value 
than  wheat  and  that  they  are  both  worth  about  15  per  cent  more  than 
barley  or  oats. 

In  feeding  grain,  as  well  as  any  other  feed,  these  comparative 
figures  should  always  be  borne  in  mind  and  serve  as  a  fundamental 
basis  in  composing  the  ration. 

SUPPLEMENTS 

Protein  Supplements. — Blood,  neither  fresh  nor  dried,  should  ever 
be  fed  to  poultry  as  it  is  not  palatable  and  not  well  digested.  Further- 
more, the  price  in  most  cases  will  be  prohibitive. 


BUL.  417]  POULTRY    FEEDING:    PRINCIPLES    AND    PRACTICE  27 

Fish  scrap  or  meal  is  the  dried  product  derived  from  the  whole 
fish,  such  as  dog-fish  or  herring,  and  from  the  waste  from  canneries. 
Pish  proteins  are  not  very  different  from  or  superior  to  proteins  of 
other  animal  products,  but  the  fish  products  generally  are  manufac- 
tured at  lower  temperatures  than  the  corresponding  meat  products. 
They  are,  as  a  consequence,  more  palatable  and  better  digested  than 
meat  scraps  or  tankage.  An  average  fish  scrap  which  contains  about 
60  per  cent  protein,  will  have  about  70  pounds  of  digestible  nutrients 
to  the  hundred.  It  is  usually  worth  about  30  per  cent  more  than  a 
meat  scrap  of  the  same  protein  content  as  shown  by  analysis.  Unless 
the  fat  content  is  far  above  the  average,  which  should  be  between  4 
and  6  per  cent,  fish  scrap,  even  when  fed  in  large  amounts,  does  not 
under  any  circumstances  give  taste  or  odor  to  the  eggs  produced  by 
flocks  to  which  it  is  fed. 

In  addition,  fish  scrap  contains  lecithin,  an  organic  substance 
which  is  supposed  to  be  very  important,  and  certain  desirable  minerals, 
like  iodine. 

Meat  scrap  and  tankage  are  very  similar  packing  house  products. 
They  represent  the  dehydrated  residue  from  fresh  meat  scraps,  bones, 
etc.,  from  which  most  of  the  fat  has  been  removed  by  boiling,  and  the 
residue  from  the  manufacture  of  boullion  cubes.  The  protein  content 
generally  is  around  50  per  cent,  but  varies  according  to  the  amount 
of  bone  contained.  The  two  products  are  also  derived  from  diseased 
animals. 

Meat  scrap  and  tankage  of  high  quality  are  excellent  feeds,  but 
very  often  in  the  form  in  which  they  are  obtained  on  the  market,  they 
have  been  overcooked  to  a  degree  that  has  injuriously  affected  their 
palatability  and  their  digestibility.  The  same  commercial  brands  often 
vary  widely  in  quality  from  time  to  time,  so  that  it  may  be  difficult 
to  obtain  a  uniform  product  over  a  long  period  of  time.  A  good 
tankage  or  meat  scrap  with  about  50  per  cent  protein  will  contain 
about  53  pounds  of  digestible  nutrients  to  the  hundred. 

Fresh  meat,  such  as  horse  meat,  is  an  excellent  feed  if  acquired 
and  fed  under  sanitary  conditions,  which  unfortunately  is  not  usually 
the  case.  Therefore  this  product  means  a  constant  menace  to  the  health 
of  the  flock.  Because  of  the  high  moisture  content,  however,  the  price 
which  is  usually  asked  is  too  high.  Assuming  about  the  same  digesti- 
bility for  fresh  meat  as  for  a  good  tankage  (meat  scrap),  the  former 
would  be  worth  not  more  than  40  per  cent  of  the  value  of  the  dried 
product,  not  counting  the  additional  labor  involved  in  feeding  the 
fresh  meat  and  the  difficulties  in  distributing  it  evenly  among  the 
birds. 


28  UNIVERSITY    OP    CALIFORNIA EXPERIMENT    STATION 

Milk  in  any  form  is  an  excellent  feed.  Very  satisfactory  produc- 
tion has  been  obtained  when  milk  has  been  fed  as  the  only  supplement 
to  grains  besides  green  feed.  (In  that  case  water  was  not  given  at 
all.)  Considering,  however,  that  skim  milk  (and  whole  milk  is  too 
expensive  to  deserve  consideration),  is  simply  a  source  of  the  ordinary 
nutrients  and  contains  no  great  amount  of  any  costly  constituents, 
such  as  vitamins,  it  is  clear  that  milk  has  to  be  compared  with  other 
feeds  on  the  basis  of  digestible  nutrients  and  price.  Such  a  com- 
parison brings  out  the  fact  that  milk  and  milk  products  generally  are 
too  expensive  to  justify  an  extensive  use  for  laying  birds,  except  in 
case  of  a  cheap  local  supply.  Because  birds  are  extremely  fond  of  it, 
however,  a  temporary  feeding  of  milk,  with  its  high  protein  content, 
in  addition  to  the  ordinary  ration,  is  a  good  stimulant  for  egg  pro- 
duction for  pullets  starting  to  lay  and  for  hens  when  production 
decreases  in  the  fall,  providing  they  are  not  losing  in  weight. 

There  is  but  little  difference  in  feeding  value  between  fresh,  semi- 
solid, and  dried  milk  products.  The  modern  process  of  manufacture 
does  not  seem  to  change  the  quality  of  the  nutrients,  so  that  the  value 
in  each  case  depends  on  the  amount  of  solids  contained.  Roughly 
speaking,  1  pound  of  dry  milk  is  equivalent  to  3%  pounds  of  semi- 
solid, or  10  pounds  of  fresh  skim  milk.  Neither  is  there  any  difference 
in  value  between  sweet  and  sour  milk.  In  order  to  avoid  digestive 
troubles,  the  milk  should  preferably  be  fed  either  sweet  all  the  time, 
or  sour  all  the  time.  It  is  generally  easier  to  feed  the  sour  milk.  The 
acidity  is,  contrary  to  general  belief,  of  no  particular  feeding  value 
to  the  bird  under  normal  conditions.  Where,  as  in  the  case  of  milk 
feeding  for  the  prevention  or  cure  of  coccidiosis,  the  lactic  acid  itself 
seems  to  be  beneficial,  the  acid  should  preferably  be  formed  from  the 
milk  by  fermentation  in  the  intestines.  The  nutrients  of  milk  are 
almost  completely  digested. 

The  oil  meals,  also  called  oil  cake  meals,  are  protein-rich  residues 
from  coconuts,  linseeds,  peanuts,  soybeans,  etc.,  which  have  had  their 
oil  extracted.  The  fat  is  removed  by  high  pressure  in  the  "old"  or 
' '  English ' '  process ;  or  by  extraction  with  a  solvent,  the  ' '  new ' '  pro- 
cess. The  "old"  process  residue  has  a  high  fat  content  and  may 
therefore  be  valuable  as  feeds  for  other  classes  of  stock,  but  only 
"new"  process  products  should  be  used  for  feeding  poultry,  as  a 
high  fat  content  cannot  be  made  use  of  by  birds  and  it  may  retard 
the  digestion  of  the  other  nutrients.  Also  the  "old  process"  (0.  P.) 
products  do  not  keep  as  well  as  the  "new  process"  (N.  P.)  products, 
because  with  a  high  fat  content  they  easily  become  rancid. 


BUL.  417]  POULTRY   FEEDING :    PRINCIPLES   AND   PRACTICE  29 

Coconut  oil  meal  is  a  fair  feed  for  poultry.  It  is  not  as  palatable 
as  the  other  products  of  this  same  class  and  is  known  to  have  caused 
digestive  troubles  in- poultry  as  well  as  in  other  farm  animals,  horses 
for  example. 

Linseed  meal  is  a  good  feed,  being  high  in  suitable  proteins. 
Because  of  its  laxative  effect  it  should  never  be  added  to  a  mash  in  a 
higher  proportion  than  5  per  cent.  Linseed  meal  is  too  high  in  price 
compared  with  its  feeding  value  to  justify  its  use  as  a  poultry  feed. 

Peanut  meal  is  one  of  the  best  of  these  protein-rich  supplements. 
Its  use  in  this  country  is  of  comparatively  recent  date,  but  it  has  been 
successfully  used  in  the  Orient  and  in  Europe  over  a  long  period 
of  years. 

Soybean  meal  is  another  very  valuable  concentrate.  Like  peanut 
meal,  it  has  only  of  recent  years  been  of  any  importance  in  this 
country.  Now  considerable  quantities  are  imported  and  steadily 
increasing  amounts  are  also  being  manufactured  in  the  United  States. 
Philips  (1925)  has  clearly  demonstrated  the  high  value  of  soybean 
meal  in  poultry  feeding  and  it  is  doubtless  gaining  in  popularity  all 
the  time.  It  contains  about  63  pounds  of  digestible  nutrients  to  the 
hundred. 

The  wheat  by-products  are  at  the  present  time  enjoying  an  alto- 
gether undeserved  popularity  as  feed  for  poultry.  They  are  all  low 
in  proteins,  and  the  protein  contained,  being  nothing  but  a  deficient 
grain  protein  itself,  is  of  course  poorly  suited  as  a  supplement  to  a 
grain  ration.  In  addition,  the  wheat  by-products  are  rich  in  a  par- 
ticular kind  of  carbohydrates?  the  pentosans,  which  are  practically 
not  digested  by  poultry.  As  a  consequence  the  wheat  by-products  are 
low  in  total  digestible  nutrients,  wheat  bran,  for  instance,  containing 
only  about  45  pounds  to  the  hundred.  The  present  prices,  therefore, 
should  exclude  these  products  from  poultry  feeds,  and  it  is  a  question 
whether  such  bulky  feeds  should  not  always,  at  any  price,  be 
fed  with  caution. 

There  is  a  popular  idea  that  wheat  bran  is  essential  for  poultry. 
This  is  not  the  case,  for  it  contains  nothing  important  that  is  not  pro- 
vided by  the  whole  grains.  The  slightly  laxative  effect,  if  it  should 
ever  be  desired,  can  just  as  well  be  obtained  from  more  efficient  feeds, 
like  linseed  meal. 

Animal  versus  vegetable  protein  supplements. — The  question  as  to 
whether  to  use  animal  or  suitable  vegetable  protein  concentrates  in 
feeding  for  growth  and  egg  production  should  largely  be  decided  by 
prices  per  unit  of  protein  in  the  different  products.  A  good  prac- 
tical rule  is  to  introduce  vegetable  protein  supplements  into  a  poultry 


30  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

ration,  when  the  price  per  unit  of  digestible  protein  in  the  vegetable 
concentrates  is  at  least  10  per  cent  less  than  for  corresponding  animal 
protein.  One  should  never  be  afraid  of  using  the-  vegetable  products, 
as  there  is  no  fundamental  difference  between  the  two  classes. 
Dougherty  (1916)  obtained  as  good  an  egg  production  with  a  mash 
containing  7.5  per  cent  meat  scrap  as  with  much  higher  concentrations 
of  animal  protein,  provided  proper  vegetable  protein  concentrates 
were  added  to  make  up  for  the  difference.  Moreover,  Wheeler  (1899) 
demonstrated  that  satisfactory  growth  and  egg  production  in  the 
domestic  fowl  could  be  obtained  on  vegetable  protein  exclusively. 
These  results  have  been  verified  by  Kennard  and  co-workers  (1922) 
and  Philips  (1925). 

While  thus  the  protein  may  be  supplied  from  vegetable  sources 
only,  there  is  one  reason  for  always  including  a  small  quantity,  say 
4  or  5  per  cent,  of  milk  products,  fish  or  meat  scraps.  These  sub- 
stances have  the  peculiar  effect,  on  entering  the  glandular  stomach, 
of  causing  a  particularly  strong  flow  of  digestive  juices,  which  must 
be  assumed  to  cause  a  more  rapid  and  complete  digestion  of  the  rest 
of  the  food. 

If  suitable  vegetable  protein  concentrates  are  used,  it  is  of  little 
concern  whether  one  product  only  is  used  or  several  concentrates  in 
combination,  variety  here  seeming  to  have  small  value. 

Mineral  Supplements. — Care  should  always  be  taken  to  ensure 
sufficient  consumption  of  minerals.  The  best  practice  is,  therefore,  to 
include  most  of  the  necessary  mineral  supplements  in  the  mash. 
Growing  and  laying  mashes  should  contain  between  8  and  10  per  cent 
of  minerals,  a  part  of  which  should  always  consist  of  calcium  car- 
bonate, such  as  ground  limestone.  This  will  aid  in  the  neutralization 
of  organic  and  inorganic  acids  produced  in  the  body. 

A  certain  part  of  the  minerals  needed  by  the  birds  is  naturally 
contained  in  the  grain  and  protein  concentrates  in  the  ration.  These 
products  do  not,  however,  provide  sufficient  sodium,  calcium,  phos- 
phorus, chlorine,  and  iron,  particularly  for  growing  and  laying  birds. 
The  deficient  minerals  can  be  easily  and  cheaply  obtained ;  sodium  and 
chlorine  from  common  salt;  calcium  from  limestone,  oyster  shell, 
ground  marble,  hydrated  lime,  etc. ;  phosphorus  and  calcium  from 
fresh  bones  or  bone  meal,  steamed  bone  meal,  acid  phosphate,  etc. 
The  iron  requirements  are  usually  taken  care  of  by  the  iron  in  the 
vitamin  supplements.  A  possible  iodine  deficiency  is  overcome  by 
using  fish  scrap  as  a  source  of  protein  or  by  using  oyster  shell  for 
supplying  calcium  carbonate. 


BUL.  417]  POULTRY   FEEDING:    PRINCIPLES   AND   PRACTICE  31 

As  Henry  and  Morrison  (1923)  point  out,  there  is  never  any  reason 
for  paying  high  prices  for  proprietary  mineral  supplements,  since  an 
adequate  supply  can  always  be  provided  very  cheaply.  Moreover, 
with  the  exception  of  green  bone  (see  below)  there  is  no  basis  for 
preference  between  the  different  sources  mentioned  for  the  particular 
minerals.  Therefore  it  will  not  be  necessary  to  discuss  them  all  indi- 
vidually, but  only  to  point  out  the  following  considerations. 

Finely  ground  common  salt  should  be  added  to  the  mash  in  the 
proportion  of  from  one-half  to  one  per  cent.  Salt  stimulates  the 
appetite,  aids  digestion,  and  is  also  required  for  other  body  processes. 
According  to  an  old  superstition,  salt  is  poisonous  to  birds.  Salt, 
however,  is  not  poisonous,  but  when  fed  in  concentrated  form  it  may 
be  injurious  to  birds  not  having  an  adequate  supply  of  water.  Under 
similar  conditions  salt  may  even  be  harmful  to  humans. 

Fresh  green  bone  is  a  good  source  of  calcium  and  phosphorus.  It 
is  very  readily  eaten  but  it  contains  too  much  fat  to  be  fed  in  large 
amounts  and  the  protein  contained,  being  deficient  in  essential  amino 
acids,  has  a  low  value.  As  usually  fed  it  is  difficult  to  get  an  even 
distribution  among  the  members  of  a  flock  and  in  addition  it  is 
extremely  difficult  to  handle  and  feed  in  large  quantities  under  sani- 
tary conditions.  It  should  not  be  considered  as  a  feed  for  flocks  in 
most  sections  of  California. 

Calcium  and  phosphorus  should  however,  always  be  included  in 
the  mash,  some  of  the  calcium  always  in  the  form  of  calcium 
carbonate  (as  in  limestone  or  oyster  shell)  to  give  the  desired  alkaline 
reaction.  If  animal  protein  concentrates  with  30  per  cent  mineral 
content  are  used,  they  supply  calcium  and  phosphorus  in  such  an 
amount  that  it  is  only  necessary  to  add  about  2  per  cent  limestone 
to  the  mash.  If  the  mineral  content  of  the  fish  or  meat  scrap  is  less 
than  30  per  cent,  sufficient  bone  meal  should  be  added  to  bring  it  up 
to  30  per  cent.  When  vegetable  protein  concentrates  are  used,  it  is 
always  necessary  to  add  both  limestone  and  bone  meal,  about  one 
pound  of  mineral  mixture  for  every  five  pounds  of  vegetable  con- 
centrates, in  the  proportions  of  40  per  cent  ground  limestone  and 
60  per  cent  steamed  bone  meal. 

Other  minerals  like  sulphur,  sulphur  compounds,  Epsom  salts, 
etc.,  are  frequently  advertised  as  highly  essential  for  birds.  They 
have  never  been  demonstrated  to  have  any  good  effect.  If  birds  are 
sick  or  out  of  condition,  they  need  specific  remedies ;  general  tonics 
are  of  no  value. 

Charcoal  should  also  be  mentioned  in  this  connection.  It  is  most 
generally  recommended  and  used  as  a  supplement  to  poultry  rations. 


32  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Much  investigational  work  has  been  carried  out  in  order  to  demon- 
strate the  benefit  of  charcoal  feeding  but  with  no  success.  It  is  cer- 
tain that  the  absorbing  power  of  charcoal  has  been  much  over- 
emphasized. Even  if  present,  the  absorbing  power  would  be  of  ques- 
tionable value.  Charcoal  feeding  for  poultry  should  be  given  up  as  an 
unnecessary  expense  just  as  it  has  been  abandoned  in  human  dietetics, 
where  it  was  formerly  recommended. 

Grit  should  be  given  to  poultry  at  all  times,  in  order  to  enable 
the  birds  to  grind  the  feed  in  an  efficient  way.  Hard  grit,  such  as 
granite  grit,  will  serve  such  a  purpose  better  than  soft  grit  like  lime- 
stone grit,  but  the  latter  can  be  used  satisfactorily.  Hard  grit  is 
absolutely  insoluble  and  consequently  does  not  supply  any  kind  of 
nourishment,  so  that  it  does  not  take  the  place  of  mineral  supplements. 

Vitamin  Supplements. — In  order  to  make  the  poultry  ration  com- 
plete, certain  vitamin  supplements  have  to  be  added.  The  vitamins  to 
which  particular  attention  has  to  be  paid,  for  the  reasons  explained 
above*  are  A  and  D.  Vitamin  A  is  commonly  supplied  by  fresh  greens 
such  as  alfalfa,  clover,  kale,  chard,  lettuce,  sudan  grass,  green  barley, 
green  oats,  young  corn,  etc.  It  may  be  supplied  equally  well  by  dried 
greens,  yellow,  carrots,  or  cod-liver  oil. 

Provided  an  abundance  of  direct  sunlight  is  available  no  further 
provision  of  vitamin  D  in  the  diet  has  to  be  made.  When  it  is  neces- 
sary to  add  vitamin  D  to  the  ration,  the  most  practical  way  at  the 
present  time  is  to  use  cod-liver  oil. 

A  regular,  plentiful  supply  of  fresh  greens  is  the  common  method 
of  supplying  vitamin  A  to  poultry.  Fresh  greens  also  supply  suc- 
culence, which,  however,  has  not  been  demonstrated  to  have  any 
value.  When  depending  upon  fresh  greens  as  a  source  of  vitamin  A, 
the  poultryman  has  to  plan  ahead  for  a  regular  every-day  supply  of 
from  5  to  6  pounds  of  green  feed  for  every  100  birds.  Much  more 
should  not  be  fed  as  the  feed  value  of  green  feed  is  too  low  to  justify 
the  expense.  An  excess  of  green  feed  also  makes  the  egg  yolks  dark, 
since  it  is  the  main  source  of  the  pigment  xanthophyll.  Tests  of 
different  fresh  greens  as  a  source  of  vitamin  A  have  shown  very  little 
difference  in  the  value  of  the  different  greens.  Therefore  the  green 
feed  which  can  be  procured  most  economically  at  any  particular  time 
or  place  should  be  used. 

Alfalfa  can  generally  be  depended  upon  during  a  large  part  of  the 
year.  It  should  preferably  be  cut  when  young  and  tender  because  the 
woody  stems  of  the  mature  plant  make  it  less  digestible  and  palatable. 
They  are  also  low  in  vitamin  A  content. 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE  33 

In  many  sections  of  California  kale  is  depended  upon  for  the 
green  feed.  Some  poultrymen  use  the  whole  plant,  running  it  through 
a  feed  chopper.  A  better  practice  probably  is  to  feed  the  leaves  only, 
as  they  are  the  most  valuable  part,  and  as  the  plant  under  those  con- 
ditions will  give  continued  growth  and  production. 

Green  barley,  in  most  sections  of  California,  is  one  of  the  best 
sources  of  fresh  greens  during  the  winter  months  when  many  other 
greens  are  not  available.  Even  in  the  coldest  weather  green  barley 
can  be  obtained  by  sprouting.  Of  the  twro  common  methods,  one  is 
that  of  ground  sprouting  out  of  doors.  The  grain  is  spread  in  thin 
layers  on  the  ground,  or  on  wooden  floors  constructed  for  the  purpose, 
and  covered  with  an  inch  of  moist  dirt  or  horse  manure  (not  poultry 
manure).  If  the  seed  is  protected  in  this  way  green  barley  has  been 
obtained  at  air  temperatures  which  for  a  short  time  were  as  low  as 
23°  F.  Barley  can  also  be  successfully  sprouted  indoors,  in  grain 
sprouters  constructed  for  the  purpose,  or  on  the  floor  of  basements, 
for  instance.  In  order  to  obtain  well  sprouted  grain  it  is  necessary 
to  provide  for  moisture,  heat,  ventilation,  and  light.  Only  the  green 
sprouts  have  any  value  as  vitamin  supplements.  Processed  grains, 
or  the  colorless  sprouts  produced  in  the  dark  have  no  such  value. 

In  order  to  supply  sufficient  vitamin  A  from  sprouted  barley  it  is 
necessary  that  30  per  cent  of  the  daily  grain  allowance?  that  is,  about 
3  pounds  to  100  birds,  should  be  sprouted.  It  must  be  considered, 
however,  that  the  sprouting  process  decreases  the  feeding  value  of  the 
grains,  so  that  this  way  of  producing  green  feeds  is  far  too  expensive 
for  any  great  length  of  time.  Moreover  there  is  a  danger  in  using 
sprouted  barley,  because  the  grains  that  do  not  sprout  during  the 
process,  deteriorate  and  may  develop  injurious  moulds  which  cannot 
be  easily  detected. 

Green  oats  can  be  used  in  the  same  way  as  green  barley,  but  in 
California  are  generally  more  expensive  with  no  compensating 
advantage. 

There  are  certain  advantages  in  using  dried  greens  rather  than 
fresh  greens  as  a  source  of  vitamin  A  for  poultry.  If  cured  under 
proper  conditions,  the  vitamin  A  content  is  not  much  lowered.  Greens 
to  be  used  dried  can  be  produced  more  cheaply  since  they  are  grown 
under  more  specialized  conditions  than  when  raised  by  each  individual 
poultryman.  Dried  greens  can  be  included  in  the  mash  and  therefore 
more  evenly  distributed  among  the  birds. 

The  proper  curing  conditions  are  rapid  drying  without  long 
exposure  to  the  sun  and  this  quick  curing  will  yield  a  product  of  a 


34  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

deep  green  color.  The  color  therefore  can  be  taken  as  the  best  prac- 
tical indication  of  the  quality.  Bleached  out  products,  that  is,  those 
which  have  lost  their  green  color,  have  no  value  as  a  source  of 
vitamin  A. 

At  present  alfalfa  meal  is  the  best  kind  of  dried  greens  and  has 
been  used  in  many  sections  with  as  much  success  as  fresh  greens.  The 
meal  made  from  leaves  and  blossoms  only  is  to  be  preferred  to  the 
ordinary  alfalfa  meal  because  the  woody  stems  have  little  value.  The 
vitamin  A  requirements  will  be  met  by  an  addition  to  the  mash  of 
10  per  cent  ordinary  good  alfalfa  meal  or  5  per  cent  of  the  meal  made 
from  alfalfa  leaves  and  blossoms.  Caution  should  be  used  in  purchas- 
ing leaf  and  blossom  meal  because  some  mills  dispose  of  their  sweepings 
under  the  name  at  a  low  price. 

It  should  be  pointed  out  that  birds  do  not  like  dried  alfalfa  until 
they  get  used  to  it.  If  they  are  switched  over  too  suddenly  to  a  mash 
containing  alfalfa,  they  may  go  off  feed,  but  when  the  change  is  made 
gradually,  dried  alfalfa  never  causes  any  trouble,  and  moreover  has  an 
advantage  in  that  it  contains  proteins  which  are  well  suited  as  supple- 
ments to  the  grain  proteins. 

If  alfalfa  meal  is  not  available,  practically  the  same  results  can  be 
obtained  by  feeding  alfalfa  hay  in  hoppers.  In  feeding  by  this 
method,  however,  the  advantage  of  even  distribution  is  lost. 

Except  that  in  most  places  clover  is  more  expensive  to  grow  than 
alfalfa,  all  the  statements  made  concerning  dried  alfalfa  apply  to 
dried  clover. 

Still  another  source  of  vitamin  A  has  been  found  to  be  yellow 
carrots.  Yellow  carrots  in  contrast  to  all  other  root  crops  have 
proved  to  be  fully  equivalent  to  fresh  greens  for  this  purpose.  They 
have  not  been  popular  as  a  poultry  feed  because  there  is  a  common 
belief  that  birds  do  not  relish  them.  Like  any  new  feed,  birds  have  to 
become  used  to  them,  but  they  do  so  quickly.  Yellow  carrots  can  fre- 
quently be  produced  more  cheaply  than  fresh  greens  and  they  also 
have  an  advantage  in  that  they  can  be  stored  for  a  time.  It  is  an 
interesting  fact  that  the  yellow  pigment  of  carrots  is  carotin,  which 
does  not  color  egg  yolks. 

The  last  vitamin  A  supplement  to  be  considered  is  cod-liver  oil. 
One-half  of  one  per  cent,  or  one-half  pint  of  tested  cod-liver  oil  added 
to  every  100  pounds  of  mash  or  of  grains  will  take  care  of  the  vitamin 
A  requirements  of  poultry.  Cod-liver  oil  lacks  important  minerals  like 
iron,  and  can  therefore  be  recommended  only  as  a  temporary  vitamin 
A  supplement,  and  then  only  if  a  high-grade  oil  is  used.    It  should  be 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE  35 

recalled  in  this  connection  that  vitamin  A  in  cod-liver  oil-  is  easily 
destroyed.  It  is  therefore  essential,  to  be  snre  of  good  results,  to  use 
an  oil  which  has  been  tested  and  found  rich  in  vitamin  A.  Ordinary 
untested  commercial  cod-liver  oils  vary  widely  and  are  undependable 
as  a  source  of  vitamin  A.  Recommendation  of  1  per  cent  cod-liver 
oil  is  commonly  made  to  allow  for  variation  of  the  vitamin  A  content 
when  untested  oils  are  used.  This  doubling  of  the  amount  hoVever  is 
no  guarantee  that  sufficient  vitamin  A  will  be  present,  so  it  is  better 
to  use  the  tested  oil  in  spite  of  the  higher  price.  Even  tested  oil 
should  never  be  mixed  into  feeds  and  stored,  as  it  then  rapidly  loses 
its  effectiveness.  The  cod-liver  oil  mash  must  be  mixed  fresh  every  day. 

Cod-liver  oil,  besides  supplying  vitamin  A,  also  supplies  vitamin  D, 
which  will  be  needed  by  young  stock  spending  a  considerable  part  of 
the  time  indoors  in  the  early  part  of  the  year  because  of  the  cool 
weather  or  rain,  and  in  the  summer  because  of  the  heat.  It  is  therefore 
always  advisable  (at  least  in  most  sections  of  California)  to  feed  cod- 
liver  oil  as  a  source  of  vitamin  D  to  young  chicks  during  the  first  6  to 
10  weeks  of  their  life.  Older  birds  need  cod-liver  oil  for  the  same 
purpose  during  long  continued  cloudy  or  foggy  weather.  Laying  birds 
may  also  need  this  additional  supply  of  vitamin  D  during  seasons  of 
very  heavy  production  and  late  in  the  season,  when  the  evidence  of 
poor  calcium  utilization  can  often  be  observed  in  the  poor  shell  texture 
of  the  eggs  produced.  Cod-liver  oil  should  also  be  fed  to  breeding 
birds  at  all  times,  not  because  it  is  always  needed,  but  as  a  precaution, 
because  it  may  be  needed  at  any  time. 

One-half  per  cent  or  one-half  pint  of  cod-liver  oil  added  to  100 
pounds  of  the  mash  or  of  the  grains,  supplies  sufficient  vitamin  D  for 
the  birds.  As  this  vitamin  is  far  more  stable  than  vitamin  A,  an  ordin- 
ary commercial  cod-liver  oil  generally  is  good  enough  for  this  purpose. 
As  mentioned  previously  particular  light  rays  present  in  direct  sun- 
light (not  passed  through  ordinary  glass),  or  in  light  from  special 
lamps  take  the  place  of  vitamin  D.  It  is  not  practical  on  commercial 
poultry  farms  to  provide  these  ultra-violet  rays  artificially  from 
mercury  quartz  lamps ;  neither  has  it  as  yet  proved  practical  to 
irradiate  feeds. 

Water. — It  is  essential  that  birds  should  at  all  times  have  access  to 
clean,  fresh  water,  except  when  milk  is  given  as  the  only  protein  sup- 
plement, in  which  case  no  water  should  be  given.  The  best  way  to 
ensure  a  continual  supply  of  fresh  water  is  to  have  running  or  drip- 
ping water  in  a  trough  or  fountain  which  should  be  so  constructed  that 
the  overflowing  water  does  not  wet  the  surrounding  litter  or  ground. 


36  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

In  hot  weather  it  may  be  necessary  to  supply  additional  drinking 
space  because  facilities  which  are  sufficient  for  ordinary  times  of  the 
year  may  not  take  care  of  the  greatly  increased  water  consumption. 
Neglecting  this  precaution  will  inevitably  check  production. 


LAYING    RATIONS 

A  laying  ration  that  has  given  good  results  in  the  hands  of  many 
poultrymen  was  recommended  by  Dougherty  (1922),  and  contains 
the  following : 

Grains  Mash 

50  pounds  yellow  corn  50  pounds  wheat  "1 

50  pounds  barley  25  pounds  yellow  corn  or  milo  I Ground 

25  pounds  barley  or  oats  J  toSetner 

Milk  kept  before  the  birds  all 
the  time  and  used  to  moisten 
mashes 

Vitamin  A  supplement  and  minerals  in  any  of  the  forms  mentioned 
have  to  be  provided  separately. 

Another  widely  used  ration  is  one  recommended  by  Payne  (1926). 
It  is  formulated  on  the  same  principle,  namely,  the  use  of  whole  and 
ground  grains  supplemented  by  protein  and  minerals.  This  ration  is 
no  better  but  at  present  price  levels  is  somewhat  cheaper.  With  slight 
modification  it  is  as  follows : 


Grains  Mash 

100  pounds  corn  or  milo  80  pounds  corn   or  milo  1 

100  pounds  wheat  or  kafir  80  pounds  wheat  or  kafir  t 

100  pounds  barley  or  oats  80  pounds  barley  or  oatsj  °^e  ner 


60  pounds  fish  or  meat  scrap  (50  per 

cent  protein) 
2  pounds  ground  limestone  or  oyster 

shell 
iy2  pounds  finely  ground  salt 

Vitamin  A  supplement  and  lime  in  any  of  the  forms  mentioned 
have  to  be  provided  separately. 

(If  fish  or  meat  scrap  contains  less  than  30  per  cent  minerals  the 
deficiency  has  to  be  made  up  by  the  addition  of  bone  meal.)  The  grain 
mixture  of  this  ration  has  the  nutritive  ratio  of  1 :6.92,  the  mash  that 
of  1 :3.86.  Grains  and  mash  combined  give  the  nutritive  ratio  of 
1 :5.39.  This  ration,  therefore,  contains  far  less  protein  than  most 
other  poultry  rations  recommended  at  the  present  time;  that  is,  the 
nutritive  ratio  is  wider  than  is  usually  the  case.  The  fact  that  this 
ration  gives  as  satisfactory  production  as  any  other,  is  an  illustration 


BUL.  417]  POULTRY    FEEDING:    PRINCIPLES   AND   PRACTICE  37 

of  the  fact  that  proteins  when  of  the  proper  kinds,  are  required  in 
much  smaller  proportions  than  is  popularly  supposed. 

Laying  Rations  with  Vegetable  Protein. — If  market  conditions 
make  such  changes  desirable,  vegetable  protein  concentrates  can  suc- 
cessfully be  substituted  for  concentrates  of  animal  origin.  This  sub- 
stitution is  easily  undertaken  by  replacing  each  3  pounds  of  animal 
concentrates  with  5  pounds  of  soybean  meal  (or  peanut  meal)  and 
1  pound  of  mineral  mixture.  Considering  the  previous  recommenda- 
tion, that  the  mash  should  always  contain  about  5  per  cent  of  fish  or 
meat  scrap,  the  ration,  making  use  of  the  maximum  amount  of 
vegetable  protein  concentrates  will  be : 

Grains  Mash 

116  pounds  corn  or  milo  80  pounds  corn   or  milo  "] 

116  pounds  wheat  or  kafir  80  pounds  wheat  or  kafir  I     Groimd 

116  pounds  barley  or  oats  80  pounds  barley  or  oats]       °^e   lcr 

15  pounds  fish  or  meat  scrap  (50  per 
cent  protein) 

75  pounds  soybean    meal    (or    peanut 

meal) 
17  pounds  mineral  mixture 
1%  pounds  finely  ground  salt 

Vitamin  A  supplement  and  lime  in  any  of  the  forms  mentioned 
have  to  be  provided  separately  (mineral  mixture,  see  page  31). 

Laying  ration  without  fresh  green  feed: 

Grains  Mash 

105  pounds  corn  or  milo  80  pounds  corn   or  milo  "1 

105  pounds  wheat  or  kafir  80  pounds  wheat  or  kafir  I    Tloun' 

105  pounds  barley  or  oats  80  pounds  barley  or  oats  I     °^e 

60  pounds  fish  or  meat  scrap 
2  pounds  limestone 
iy2   pounds  salt 

16  pounds  alfalfa  leaves  and  blossoms 

Lime  in  any  of  the  forms  mentioned  has  to  be  provided  separately. 
This  mash  should  be  fed  dry,  as  any  other  mash ;  there  is  no  need 
of  moistening  the  alfalfa  meal. 

CHICK   RATIONS 

There  is  no  fundamental  difference  between  a  laying  ration  and  a 
growing  ration  for  poultry.  As  Wheeler  (1909)  pointed  out,  the 
protein  requirements  of  rapidly  growing  chicks  (that  is,  up  to  the  age 
of  14  to  16  weeks)  are  as  high  or  higher  than  the  protein  requirements 
of  laying  hens.  Since  no  investigational  work  has  ever  been  done  that 
upsets  Wheeler's  conclusions,  which  moreover  are  in  close  agreement 


38 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


with  the  general  principles  of  nutrition,  it  is  a  surprising  fact  that 
most  chick  mashes  on  the  market  at  the  present  time  contain  less  pro- 
tein than  do  laying  mashes.6  Some  poultrymen  go  so  far  as  to  start 
chicks  on  grain  alone,  a  practice  which  is  unsound  because  of  the 
deficient  protein  and  mineral  content. 

There  is  no  apparent  reason  why  the  laying  rations  previously 
recommended  should  not  also  be  excellent  chick  rations,  when  cod-liver 
oil,  as  recommended  above  for  young  stock,  is  added  and  the  whole 
grains  are  reduced  to  suitable  size.  It  should  be  mentioned,  however, 
that  this  station  has  as  yet  been  unable  to  test  these  rations  on  young 


e  Theoretical  considerations  strongly  suggest  the  advisability  of  feeding 
more  protein  to  baby  chicks  than  to  laying  birds.  Bunge  (1905)  has  pointed 
out  the  close  relationship  between  the  rate  of  growth  of  different  animals  and 
the  protein  content  of  the  mother's  milk.  This  relationship  is  apparent  from 
the  following  figures,   obtained  from  Bunge,   and  Ellenberger   and  Scheunert: 


Animal 

Days  required  for 

doubling  initial 

weight 

Per  cent  protein 
in  mother's  milk 

Nutritive  ratio  of 
mother's  milk 

Man 

180 

1.6 

1  :8.6 

Horse 

60 

2.0 

1  :4.2 

Cow 

47 

3.5 

1  :3.8 

Goat 

22 

3.7 

1  :3.6 

Sheep 

Hog 

Dog 

Rabbit 

15 

14 

9 

6 

4.9 

6.1 

9.7 

15.5 

1  :3.4 
1  :3.0 
1  :2.5 
1  :  1.5 

It  is  quite  evident  that  the  rate  of  growth  during  early  life  is  directly  pro- 
portional to  the  per  cent  of  protein  in  the  natural  food,  and  consequently  to 
narrowness   of  the  nutritive  ratio. 

By  determining  the  protein  retention  at  different  ages  Bunge  was  also  able 
to  demonstrate  that  the  protein  requirements  decreased  as  the  rate  of  growth 
progressively  slowed  down.  At  the  same  time  carbohydrate  requirements 
increased  in  direct  proportion  to  the  increasing  size  of  the  animal. 

Absorbed  egg  yolk,  which  furnishes  chicks  with  their  first  nutriment  after 
hatching,  has  a  protein  content  of  about  44  per  cent  and  a  nutritive  ratio  of 
1:2.5.  Mitchell,  Card  and  Hamilton  (1926)  have  recently  shown  that  Plymouth 
Bock  chicks  double  their  initial  weight  in  14  to  15  days,  which  is  about  the 
time  required  by  a  pig. 

When  one  considers  the  fact  that  the  pig  at  birth  is  many  times  larger 
than  the  chick  at  hatching,  and  so  requires  a  larger  proportion  of  energy 
nutrients  (carbohydrate  or  fat)  than  chicks,  the  implication  is  very  strong 
that  a  chick  ration  should  be  much  narrower  than  popularly  supposed,  narrower 
to  begin  with  in  fact,  than  at  any  other  time  of  life.  It  is  also  implied  that  the 
ration  should  be  gradually  widened  as  chicks  grow  and  the  rate  of  growth 
progressively  slows  down. 

This  may  be  accomplished  by  feeding  mash  only  for  the  first  ten  days  and 
then  introducing  small  and  progressively  increasing  proportions  of  grain. 
Since  the  mash  recommended  in  this  bulletin  has  a  nutritive  ratio  of  approxi- 
mately 1  to  3.9,  such  a  practice  would  appear  fairly  conservative. 

This  matter  is  being  put  to  a  comparative  test  at  University  Farm.  As  a 
matter  of  fact  while  this  bulletin  was  being  written  it  came  to  the  writers' 
attention  that  the  practice  suggested  above  had  been  used  with  gratifying 
success  for  at  least  three  years  in  San  Diego  County. 


BUL.  417]  POULTRY    FEEDING  :    PRINCIPLES    AND    PRACTICE 


39 


stock.     Caution  therefore  is  urged  not  to  use  them  on  large  numbers 
of  chicks,  before  results  from  smaller  tests  have  been  obtained. 

For  the  use  of  poultrymen  who  prefer  to  use  standard  rations,  the 
following-  are  samples,  many  more  of  which  could  be  given :  a 
(Dougherty  1922),  b  (Payne  1926),  c  (Vandervort  1925)  and  d 
(Heuser  1920,  and  Rice  and  Botsford  1925). 


Grains 
33%  pounds  cracked  wheat 
33%  pounds  cracked  yellow  corn 
33%  pounds  steel  cut  oats 


Mas  /* 
25  pounds  bran 
25  pounds  shorts 
20  pounds  yellow  corn  meal 
10  pounds  soybean  meal 
15  pounds  meat  scrap  (or  fish  scrap) 
5  pounds  bone  meal 


Grains 
50  pounds  finely  cracked  corn 
30  pounds  finely  cracked  oats 
20  pounds  pine-head  or  steel 
cut  oats 


Mash 

33%  pounds  bran 

16%  pounds  flour  middlings  or  stand- 
ard wheat  middlings 

16%  pounds  ground  rolled  oats  or 
sifted  ground  oats 

16%  pounds  finely  ground  yellow  corn 

16%  pounds  finely  ground  meat  scrap 

Salt,  1  per  cent  of  mash 


Grains 
60  pounds  cracked  corn 
20  pounds  cracked  kafir  or  pin- 
head  oats 
20  pounds  cracked    wheat 


Mash 
30  pounds  bran 
30  pounds  shorts 
25  pounds  corn  meal 
10  pounds  meat  scrap 

5  pounds  mineral  mixture 

1  pound  salt 


Grains 
50  pounds  cracked  corn 
30  pounds  cracked  wheat 
20  pounds  pin-head  or  steel  cut  oats 


Mash 
20  pounds  wheat  bran 
20  pounds  middlings 
25  pounds  yellow  corn  meal 
10  pounds  oats 
10  pounds  meat  scrap 

5  pounds  bone  meal 
10  pounds  dried  milk 
%  pound  finely  ground  salt 

1  per  cent  cod-liver  oil 


40  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


FEEDING    METHODS 

Feeding  of  Chicks. — Baby  chicks  should  not  be  fed  before  they  are 
from  36  to  48  hours  old,  neither  should  the  feeding  be  started  very 
much  later.  They  may  be  given  lukewarm  water  before  this  time,  a 
practice  which  is  particularly  advisable  in  hot  weather.  It  is  also  good 
practice  to  keep  the  chicks  on  a  bare  wooden  floor,  or  on  floor  covered 
with  burlap,  until  after  they  are  fed  for  the  first  time. 

There  are  several  methods  used  in  starting  to  feed  chicks.  While 
certain  poultrymen  start  their  chicks  off  on  grain  only,  for  the  first 
7  to  10  days  the  growing  practice  is  that  chicks  be  fed  grain  as  well 
as  mash  and  vitamin  supplements  from  the  start.  The  amounts  of 
mash  and  grain  should  be  at  least  equal  and  it  is  a  question,  as  noted 
above,  whether  we  may  not  go  even  further  in  emphasizing  the  mash 
(see  footnote,  page  38).  A  good  practice  has  been  developed  in  south- 
ern California.  The  chick  grains  are  mixed  with  the  mash  to  form  a 
combination  feed  and  kept  before  the  birds  all  the  time  for  the  first 
ten  days.  After  this  time  grains  and  mash  are  fed  separately.  This 
method  of  feeding  also  enables  the  smaller  and  more  timid  chicks  to 
get  a  good  start  by  getting  their  supply  of  a  proper  ration. 

If  the  vitamin  supplements  are  given  in  the  form  of  fresh  greens, 
it  is  customary  to  feed  as  much  as  the  chicks  will  eat  at  least  once  a 
day.  The  birds  should  under  any  circumstance  consume  1  part  of 
tender  greens  by  weight  for  every  4  parts  of  the  other  feed.  If  dried 
greens  are  supplied,  5  per  cent  alfalfa  leaf  and  blossom  meal  or 
10  per  cent  of  good  alfalfa  meal  should  be  added  to  the  mash. 

It  has  generally  been  considered  essential  to  feed  only  small 
quantities  at  a  time  and  to  feed  frequently.  Recommendations  have 
been  made  in  the  past  to  feed  only  as  much  at  a  time  as  would  be 
cleaned  up  within  ten  or  twenty  minutes,  so  as  to  always  keep  the 
birds  hungry.  This  method,  when  properly  used,  gives  excellent 
results,  but  it  has  now  been  clearly  demonstrated  that  it  is  just  as  well, 
and  perhaps  even  better  for  the  inexperienced  poultryman,  to  have 
the  dry  mash  in  front  of  the  chicks  all  the  time  and  to  feed  the  grains 
in  small  quantities  three  or  four  times  a  day.  The  chicks,  as  well  as 
birds  of  all  other  ages,  prefer  the  grains  and  will  eat  only  as  much 
mash  as  is  necessary  to  satisfy  their  worst  hunger.  It  is  therefore 
always  possible  to  regulate  the  feed  consumption  by  regulating  the 
amount  of  grain  fed. 


BUL.  417]  POULTRY   FEEDING  :    PRINCIPLES   AND   PRACTICE  41 

As  to  the  amounts  of  feed  to  be  given  to  chicks  at  different  ages, 
no  definite  figures  can  be  given.  The  food  requirements  vary  with 
different  lots  of  birds,  with  the  weather  and  with  management.  Closely 
confined  chicks,  for  instance,  will  not  eat  as  much  as  chicks  given 
unlimited  liberty.  Therefore  successful  feeding  of  chicks  depends  on 
good  personal  judgment.  If  this  judgment  is  deficient  or  altogether 
absent,  no  rules  can  be  formulated  that  would  cover  even  a  minority 
of  the  different  conditions  and  possibilities.  On  the  average,  mash 
and  grains  during  the  first  ten  to  twelve  weeks  should  be  fed  in  equal 
proportions,  but  it  may  be  necessary  to  deviate  from  this  rule,  at  one 
time  in  one  direction,  at  another  in  the  opposite.  The  aim  is  to  keep 
the  chicks  as  healthy  and  lively  as  possible.  With  good  chicks  and 
good  weather  this  is  comparatively  easy,  but  during  bad  weather  and 
with  poor  chicks  it  may  be  more  difficult  to  keep  the  birds  as  active  as 
is  desirable.  One  method  of  doing  this,  which  should  be  used  for  only 
a  few  days  at  a  time,  is  to  feed  mash  sparingly  and  to  let  the  chicks 
work  for  the  scratch  grain  most  of  the  time.  Under  such  conditions 
it  is,  of  course,  a  necessity  to  restore  the  nutritive  balance  by  feeding 
more  mash  than  grains  as  soon  as  possible. 

With  only  a  small  number  of  chicks  it  is  comparatively  easy  to 
determine  fairly  accurately  the  amount  of  mash  consumed  every  day 
by  weighing  back,  and  then  feed  grain  accordingly.  With  larger 
numbers  of  birds  this  is  hardly  practical,  and  less  accurate  estimates 
will  usually  have  to  suffice. 

While  the  grain  portion  during  the  first  two  or  three  weeks  has  to 
be  divided  up  and  fed  from  three  to  four  times  a  day,  the  grain  feed- 
ing later  on  can  be  limited  to  mornings  and  evenings  only.  The  equal 
proportions  of  grain  and  mash  should  be  maintained  up  to  the  twelfth 
week,  the  grain  feeding  thereafter  should  be  gradually  increased  and 
the  mash  feeding  correspondingly  decreased,  since  from  this  time  until 
laying  the  protein  requirements  go  down  because  of  the  slowing  down 
of  rate  of  growth.  At  from  fourteen  to  sixteen  weeks  the  chicks  should 
have  approximately  two-thirds  grain  and  one-third  mash,  with  the 
mineral  mixture  given  on  page  31  hopper-fed  and  a  vitamin  A  supple- 
ment provided.  At  sixteen  weeks  of  age,  if  raised  properly,  Leghorn 
pullets  should  weigh  2y2  pounds  or  more.  After  sixteen  weeks  of 
age,  according  to  the  development  of  the  birds,  it  may  be  necessary  to 
feed  even  more  grain,  possibly  as  much  as  85  per  cent  grain  with  only 
15  per  cent  mash,  which  is  easily  accomplished  by  feeding  mash  only 
two  half -days  a  week. 

It  must  be  pointed  out,  however,  that  the  success  of  developing 
pullets  will  depend  entirely  upon  uniformity  of  the  flock.     The  birds 


42  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

have  to  be  selected  for  size  and  development  and  fed  in  separate 
groups.  Otherwise  more  harm  than  good  may  be  done  in  trying  to 
regulate  the  growth. 

This  is  a  good  time  to  break  the  birds  in  on  barley  and  others  of 
the  less  palatable  grains,  if  this  has  not  been  done  before.  It  is  then 
practical  to  hopper-feed  these  grains  and  to  feed  the  more  attractive 
grains  in  the  morning  and  at  night. 

Provided  the  birds  are  well  developed,  it  should  be  realized  that 
grain  feeding  during  this  time  can  hardly  be  overdone.  The  birds 
will  be  held  back  from  premature  laying  and  be  given  a  chance  to 
mature  physically,  a  condition  which  is  altogether  essential  if  the  best 
results  are  to  be  obtained  later  on.  This  method  of  management  also 
tends  to  do  away  with  an  excess  of  too  small  eggs  during  the  pullet 
year.  The  pullets  will,  of  course,  get  more  or  less  fat  in  this  way,  but 
pullets  bred  for  production  can  hardly  get  too  fat.  It  is  the  fat  that 
enables  them  later  on  to  stand  the  strain  of  egg  production  over  a  long 
period,  and  that  carries  them  over  the  beginning  of  production  until 
their  digestive  tract  has  adapted  itself  to  the  increased  demands  on  its 
activity. 

The  common  practice  of  feeding  more  bran  during  this  time  is 
not  good.  The  bran  certainly  will  retard  sexual  maturity,  but  it  will 
tend  to  stunt  the  birds  physically  also,  at  a  time  when  their  growth 
should  be  promoted. 

The  feed  consumption  of  pullets  from  the  start  up  to  maturity  is 
approximately  28  pounds  of  grain  and  mash,  more  than  two-thirds  of 
the  amount  being  grain.  During  all  this  time,  care  should  be  taken 
to  ensure  a  sufficient  supply  of  vitamin  A  supplement,  preferably  in 
the  form  of  alfalfa  or  clover,  hopper  feeding  the  mineral  mixture  (see 
page  31)  to  which  5  per  cent  salt  has  been  added. 

Feeding  Laying  Birds. — When  pullets  (Leghorns)  have  reached 
the  age  of  five  and  a  half  or  six  months  they  should  weigh  3%  pounds. 
They  should  again  be  selected  for  maturity  and  those  that  are  under- 
sized should  be  developed  further  or,  preferably,  be  marketed.  As 
far  as  the  others  are  concerned,  production  may  be  allowed  to  begin. 
Production  at  this  time  is  brought  on  simply  by  changing  the  ration 
back  to  half  grain  and  half  mash.  Temporarily  mash  may  be  fed  even 
in  slight  excess  of  the  grains.  Laying  will  normally  start  within  ten 
to  fourteen  days  of  the  change. 

From  that  time  until  the  end  of  the  first  laying  year  the  feeding 
must  be  regulated  according  to  the  production.  The  feed  consumption, 
of  course,  will  depend  upon  the  digestibility  of  the  ration  and  will  also 
vary  with  the  production.     On  an  average,  however,  a  Leghorn  hen 


BUL.  417]  POULTRY   FEEDING:    PRINCIPLES   AND   PRACTICE  43 

will  eat  in  a  year  from  70  to  75  pounds  of  grain  and  mash  together, 
which  means  that  approximately  10  pounds  of  grains  and  10  pounds  of 
mash  should  be  fed  each  day  to  a  hundred  birds. 

By  feeding  the  grain  and  mash  in  equal  proportions,  production 
Will  reach  a  certain  point.  If  the  same  feeding  is  continued,  the  birds 
may  not  be  able  to  stand  the  strain  and  will  soon  start  losing  weight 
and  finally  go  out  of  production.  They  may  even  go  into  a  molt.  On 
the  other  hand  on  this  same  ration  other  flocks  may  never  come  up  to 
a  satisfactory  production  and  may  even  put  on  fat. 

Here  the  art  of  feeding  comes  in.  It  will  be  found  that  if  birds 
lay  too  well  for  their  physical  capacity,  they  will  inevitably  lose  body 
weight.  The  maximum  point  of  production  for  a  given  flock  has  to 
be  recognized  by  the  poultryman  either  by  means  of  an  intimate  knowl- 
edge of  them  or  by  weighing  a  few  birds  from  time  to  time,  the  feeding 
being  regulated  accordingly.  If  birds  are  losing  weight  because  of 
too  heavy  production,  more  grain  should  be  fed.  The  protein  propor- 
tion is  thereby  decreased ;  production  will  go  down,  and  the  increased 
carbohydrates  and  fats  will  cause  the  birds  to  take  on  weight  and 
gain  in  power  of  resistance. 

If,  on  the  other  hand,  production  is  unsatisfactorily  low  and  the 
birds  seem  to  get  heavy  and  lazy,  a  cut  in  their  grain  allowance  will 
increase  the  consumption  of  mash,  thereby  increasing  the  propor- 
tion of  protein  consumed,  and  stimulating  activity,  appetite,  and 
production. 

Thus  it  appears  in  this  connection,  there  are  two  frequent  causes 
for  a  decrease  in  egg  production.  First,  a  breakdown  due  to  too  much 
protein  resulting  in  too  heavy  production;  second,  too  wide  a  ration 
resulting  in  the  birds  getting  too  fat.  Molting  of  pullets  in  the  fall 
and  spring  is  frequently  a  natural  reaction  against  forced  production. 

Figure  6  illustrates  records  of  feed  consumption  and  egg  produc- 
tion in  a  flock  of  birds  in  California.  The  decrease  of  production 
from  the  first  of  October  to  the  first  of  December  was  probably  due 
to  wrong  feeding  methods.  Pullets  starting  to  lay  should  have  been 
brought  into  a  condition  in  which  they  would  stand  at  least  as  much 
mash  as  grain  during  the  first  month  or  so,  with  a  resulting  produc- 
tion of  at  least  40  or  45  per  cent.  Since  these  birds  showed  a  decrease 
in  production  and  were  getting  more  grain  than  mash,  they  were 
probably  getting  fat,  and  should  have  been  forced  to  eat  more  mash. 
After  the  first  of  December  the  production  went  up — as  would  be 
expected — and  reached  its  maximum  about  the  first  of  April.  That 
this  maximum  was  beyond  the  physical  capacity  of  the  birds  is  clearly 
shown  by  the  marked  decrease  of  production  and  mash  consumption 


44 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


and  the  increasing  grain  consumption.  If,  therefore,  the  birds  had 
started  on  more  mash,  but  had  been  given  more  grains  during  the  time 
from  January  to  July,  a  more  even  production  on  a  higher  plane 
would  normally  have  resulted.  The  birds  would  then  also  have  been 
in  such  good  physical  condition  that  from  July  on  they  would  have 
been  able  to  stand  a  temporary  forcing  by  means  of  increased  mash 
feeding,  the  result  of  which  would  have  been  an  extended  laying 
period. 


Lbs. 
7 


ngrLe 

> 

* 

». 

•**. 

/ 

,<<- 

Prodcn 

rrion 

\ 

60 

1 

/ 

/ 

Mash, 

t 

\ 

\ 

A 

:>. 

/ 

^~***>* 

\ 

\\ 

/ 

K 

Grain 

A 

30 

ZO 

O 

Jan. 


Apr.         Mau        June      July  Aug.      5ep+. 


Fig.  6. — Records  of  feed  consumption  and  egg  production  in  a  flock  of  birds 

in  California. 


All-mash  or  Combination  Feeding. — During  recent  years  the  new 
practice  of  feeding  all  the  grain  finely  ground  and  mixed  together 
with  the  mash  is  being  advocated.  This  method  of  feeding  is  still  in 
an  experimental  stage,  so  that  the  final  word  cannot  be  said  about  it. 
There  are,  however,  definite  objections  to  such  a  practice.  The  nutri- 
tive requirements  of  the  same  flock  are  not  the  same  at  different  times, 
much  less  the  requirements  of  the  different  individual  birds.  Feeding 
mash  only  leaves  no  opportunity  for  variations  without  changing  the 
proportions  in  the  mixture,  making  frequent  changes  for  the  flock 
impractical  and  variations  by  the  individuals  impossible.  The  feeding 
of  grains  and  mash  separately  enables  the  individual  bird  to  influence 
its  own  ration  by  eating  more  of  one  or  the  other,  thereby  more  or  less 
meeting  its  individual  needs.  An  instinctive  ability  of  the  bird  to  do 
this  has  been  demonstrated  by  Pearl  and  Fairchild  (1921)  with  flocks 
fed  all  feeds  on  the  cafeteria  style. 


BUL.  417]  POULTRY   FEEDING:    PRINCIPLES    AND   PRACTICE  45 

It  is  quite  true  that  an  ' '  all-mash ' '  method  of  feeding  decreases  the 
labor  to  some  extent.  This  advantage,  however,  may  be  more  than 
offset  by  the  diminished  personal  attention  that  will  be  given  to  the 
birds.  Regular  feeding  hours  every  day  are  an  inducement  to  the 
poultryman  to  give  his  birds  some  of  the  care  that  can  only  be  the 
result  of  personal  contact.  Such  personal  contact  and  attention,  or 
lack  of  them,  often  determine  the  success  or  failure  of  the  poultry 
venture. 

Feeding  of  Breeding  Birds. — The  production  of  hatching  eggs,  as 
far  as  feeding  methods  are  concerned,  is  ordinarily  attained  by  the 
same  methods  as  that  of  commercial  eggs.  Frequently  birds  from 
which  the  eggs  are  collected  for  hatching  purposes  are  fed  less  protein 
in  order  to  keep  production  down  to  some  extent.  The  benefit  of  this 
practice  is  doubtful,  although  it  may  be  advisable  to  reduce  production 
previous  to  the  hatching  season. 

Certain  poultrymen  claim  to  obtain  better  hatching  eggs  when 
milk,  either  fresh  or  dried,  is  included  in  the  feed.  A  liberal  supply  of 
vitamin  A  and  vitamin  D  supplements  in  any  of  the  forms  recom- 
mended should  always  be  provided. 

Feeding  of  Molting  Birds. — Ordinarily  not  all  birds  in  a  flock  are 
molting  at  the  same  time.  Special  consideration  to  the  feeding  of 
molting  birds  therefore  is  effective  only  if  the  molters  are  separated 
from  the  other  birds.  In  that  case  the  molters,  if  they  have  the  proper 
weight,  do  not  need  as  much  feed  as  laying  birds,  but  they  should  be 
fed  well.  They  should  preferably  be  kept  in  a  quiet  place  since  they 
are  very  easily  disturbed  because  of  the  increased  sensitivity  of  the 
skin.  It  may  be  a  good  practice  to  aid  the  feather  growth  by  including 
in  the  mash  substances  rich  in  sulphur,  such  as  hydrolyzed  hoof  and 
hair  meal,  or  hydrolyzed  feathers. 

Feeding  Birds  for  Fattening. — In  common  usage  the  term  is  used  in 
referring  both  to  the  fattening  of  mature  birds  for  market  and  to  the 
forced  growth  of  young  stock  for  market.  In  one  case  the  formation 
of  fat  is  required  and  in  the  other  the  formation  of  muscle,  but  the 
rations  which  are  commonly  used  are  practically  identical.  They  are 
composed  of  ground  grains  moistened  with  milk  into  a  sloppy  soup. 
This  brings  about  the  desired  effect  by  virtue  of  the  fact  that  birds 
will  eat  more  of  a  wet  mixture  than  of  dry  food  and  will  digest  it  more 
quickly.  If  milk  is  not  available,  meat  scrap  is  used  instead  and  the 
mixture  is  moistened  with  water. 

This  is  a  branch  of  the  poultry  industry  which  can  for  several 
reasons  be  better  undertaken  by  people  who  specialize  in  this  par- 


46  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

ticular  field.  It  needs  particular  skill  and  experience,  and  can  also 
be  more  efficiently  undertaken  on  a  large  commercial  scale  near  the 
market  than  in  small  lots  on  individual  ranches  at  a  distance  from  the 
market.  If  special  conditions  make  it  advisable  for  the  individual  to 
fatten  his  birds  before  marketing  them,  the  nutritive  ratio  should  be 
adapted  to  the  kind  of  grain  required.  In  the  case  of  broilers  the 
nutritive  ratio  should  be  about  1  to  4,  and  any  combination  of  the 
ordinary  feeds  which  will  give  this  ratio  may  be  used.  For  fatten- 
ing mature  birds,  however,  the  feed  should  be  so  chosen  as  to  give  a 
wider  nutritive  ratio. 

Commercial  Poultry  Feeds. — For  many  years  commercial  feed 
mixtures  have  had  a  large  place  in  the  poultry  industry  of  California. 
This  fact  seems  to  indicate  that  they  are  serving  a  very  useful  purpose. 
Whether  in  a  given  case  it  is  better  for  the  poultryman  to  mix  his 
own,  or  purchase  ready  mixed  feeds  is  largely  an  economic  question. 

The  feed  dealer  has  the  advantage  of  buying  feedstuffs  and  mixing 
feeds  in  large  quantities.  Not  infrequently  he  can  lay  his  products 
down  in  the  poultryman 's  feed  house  as  cheap  or  cheaper  than  the 
latter  can  by  doing  his  own  mixing.  This  leaves  the  poultryman  free 
to  devote  his  whole  time  to  the  management  of  his  flock. 

The  decision  as  to  whether  commercially  mixed  or  home-mixed 
feeds  are  to  be  employed  in  a  given  instance  is  a  matter  of  business 
judgment  and  common  sense,  provided  always  that  the  principles  out- 
lined above  have  been  followed  reasonably  closely. 

It  has  been  pointed  out  and  indeed  emphasized  that  there  is  no  one 
best  ration.  Any  ration  which  provides  the  proper  kinds  and  propor- 
tions of  nutrients  as  economically  as  possible  is  a  good  ration.  There 
is  no  reason  to  believe  that  anyone  can  do  more  than  this.  There  does 
not  appear  to  be  much  foundation  for  large  claims  concerning  secret 
formulae  or  particular  substances. 


BUL.  417]  POULTRY   FEEDING :    PRINCIPLES   AND   PRACTICE  47 


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1905.     Lehrbuch    der    Physiologie    des    Menschen,    Vol.    II,    2nd    edition, 
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